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Heater Control Valve (Duo-Valve) Disassembly and Cleaning
 
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Pelican Technical Article:

Heater Control Valve (Duo-Valve) Disassembly and Cleaning

Jared Fenton

Time:

1 hour1 hr

Tab:

$0

Talent:

***

Tools:

T15 Torx driver, pliers

Applicable Models:

Mercedes-Benz W210 (1996-03)

Parts Required:

Duovalve, coolant

Hot Tip:

Drain a small amount of coolant from the system.

Performance Gain:

heater works better.

Complementary Modification:

Replace coolant.

The climate control system on the W210 Chassis Mercedes has a dual climate system. What this means is that one side of the car can be cool, while the other side blows warm air and vice-versa. The Duovalve is used to regulate the amount of engine coolant that flows into the heater core between both sides of the passenger compartment.

The Duovalve can fail in a few different ways. The upper electronic portion that holds the coils can develop an internal fault, rendering them inoperative. Usually, there is a break in the coil windings where the wiring meets the electrical connector on the chassis. This is essentially two valves inside a casing that, over time, can become blocked with corrosion from the engine coolant, preventing the valves from closing. In this case, you would get hot air blowing from one or both of the vents at the same time.

The Duovalve can also fail when the small pintle shafts break inside the bottom housing. When this happens, the valve can stick open. Additionally the inside of the two coils can become blocked with corrosion from the engine coolant, preventing the valves from closing. In both cases, you would get hot air blowing from one or both of the vents at the same time.

In this article, we will go over the steps involved with disassembling the Duovalve and replacing it, if needed.

Shown here is the Duovalve, which is mounted on the right side of the car, just above the upper mounting point for the front shock.
Figure 1

Shown here is the Duovalve, which is mounted on the right side of the car, just above the upper mounting point for the front shock.

This picture shows the location of the five T15 Torx screws which hold the upper portion of the Duovalve to the lower portion (green arrows).
Figure 2

This picture shows the location of the five T15 Torx screws which hold the upper portion of the Duovalve to the lower portion (green arrows).

Carefully remove the five screws.
Figure 3

Carefully remove the five screws. It helps to use a magnetized screwdriver. This will prevent you from dropping the screws under the valve. Retrieving the screws from underneath can be a real pain. Once all the screws are removed, VERY carefully pull the magnetic coils up and off the valve. You'll want to apply equal pressure to each side of the coils. Once free, remove the electrical connector.

Sometimes, the inner sealing plate will be stuck inside the coils due to corrosion.
Figure 4

Sometimes, the inner sealing plate will be stuck inside the coils due to corrosion. What you should see are the two pintle valves inside the bottom half of the Duovalve. In our case, you can see where the shaft of the left valve has broken off (green arrow), leaving the valve cocked in place and the heater blowing hot all the time on one side of the car. In this instance, you will need to replace the whole valve or try to repair the shaft. I've heard of some people using a rivet to repair the shaft and others using high strength epoxy, and then sanding the shaft down.

In this picture you can see the inner sealing plate still stuck to the bottom of the Duovalve.
Figure 5

In this picture you can see the inner sealing plate still stuck to the bottom of the Duovalve. Very carefully pull the two shafts up and out of the plate (green arrows). Make sure that you also retain the springs on the ends of these valves. Once the shafts are removed, carefully apply equal pressure to each side of the plate to remove it (purple arrows).

Here is where you want to check for corrosion or any buildup (green arrow).
Figure 6

Here is where you want to check for corrosion or any buildup (green arrow). The plunger shaft should be able to move inside the coil with no resistance.

Here is the procedure for replacing the entire Duovalve.
Figure 7

Here is the procedure for replacing the entire Duovalve. Begin by clamping off the water hose leading to the Duovalve from the outside of the cowl panel, as shown here.

Use a pair of channel locks to loosen and slide back the hose clamp holding the water hose to the Duovalve.
Figure 8

Use a pair of channel locks to loosen and slide back the hose clamp holding the water hose to the Duovalve.

Once the hose clamp is off, carefully peel off the water hose and push the grommet molded into the hose out of the cowl panel.
Figure 9

Once the hose clamp is off, carefully peel off the water hose and push the grommet molded into the hose out of the cowl panel. Be prepared for a little bit of coolant to spill out of the hose and Duovalve.

There are two metal clips on either side of the housing that hold the Duovalve in place (green arrows).
Figure 10

There are two metal clips on either side of the housing that hold the Duovalve in place (green arrows). This picture shows the Duovalve removed to give you a better view of the clips. Pull each clip outwards until they stop. Now lift the Duovalve up and out of the housing. It will take a little effort to release it from the bottom. Try to pry it up from the bottom of the Duovalve (yellow arrow), but use caution not to break the lower plastic housing.

Press the metal tabs on the housing back inside (green arrows).
Figure 11

Press the metal tabs on the housing back inside (green arrows). This prepares the housing to accept the new Duovalve.

Shown here are the catches on the Duovalve (green arrows).
Figure 12

Shown here are the catches on the Duovalve (green arrows). These slide over the catches in the housing, locking it in place. Now take the new Duovalve and press it down into the housing until both sides click into place. Re-connect the hoses and electrical connectors and you're done.


NOTES:





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Comments and Suggestions:
GREGM Comments: I have a 2006 E350 W211 and when A/C is turned on am experiencing warm air from driver's vents and cool air from passenger. If at night time driver's side somewhat cool but during day in 80+ degree temps acts more like on "vent" then A/C. Local tech said possible the A/C drier needing replacement. Any insight would be appreciated. - GREG
December 7, 2016
Bergie Comments: Hi Nick. I read it from the ac display unit . There are also no fault code shown on the display. It is item 7 on the list which is pressure in the ac.See comments of Larry on 2 Nov 2014 which discussed the same issue with you. Thanks for your help. What must the pressures be in bar on low and high in the merc ac?
September 23, 2016
  Followup from the Pelican Staff: Pressure depends on ambient temp. normal summer, 30 low 200 high, in psi. You'll have to convert. - Nick at Pelican Parts  
Bergie Comments: Hi Pelican staff. Have a E 270 cdi 2001. The value for ac pressure on the ac display shows 6. what does the value mean and . Does it need top up. What should the value be? Thanks
September 22, 2016
  Followup from the Pelican Staff: I am not sure. Where are you reading this value? - Nick at Pelican Parts  
Roger Comments: Hello Pelican Team.
My car: W210 300 TD 1997, 420.000 km, it works fine, I have to fix the duovalve now inside left-fresh, inside-right hot, so a lot of thanks for your very good explanations.
Question: wouldn't it be easier to take out the entire duovalve from its place, then dismount it and work on it at workshop or at home kitchen... and finally re-mount once repaired?
Kind regards,
Roger
August 7, 2016
  Followup from the Pelican Staff: Sure, that is an Ok method. Just don't get coolant near where you eat in the kitchen. - Nick at Pelican Parts  
Julian Comments: Hi
Can you clarify re the coolant replacement please - if I unscrew the duovalve - does coolant leak out? - a little? - or flood out? - does the radiator then need to be refilled? - or topped up? - or not essential?
Also what voltage should I be reading on the connector? - should I be able to read voltage when uplugged from the valve?
Thanks
Regards
Julian
June 5, 2016
  Followup from the Pelican Staff: When the duo-valve is opened, all the coolant up to that level will drain.

You didn't mention what vehicle you have, So I have to guess at the voltage. Likely 12 volts and ground at the connector. - Nick at Pelican Parts
 
T Bone Comments: I have a 2005 E320 Mercedes sedan. A/C works fine. Only outside air comes through the vents when turned on upper and lower. However, the defroster does heat up really good about every other time I turn the car on. Any suggestions on the cause and fix?
April 10, 2016
  Followup from the Pelican Staff: I would assume there is an issue with the mode doors. Start by checking the vehicle for fault codes. - Nick at Pelican Parts  
Bob Comments: 2008 MB S550. Climate control is set to auto. After driving 30-45 minutes the climate control goes into max AC and blows cold air its about 40 Degrees outside. Even if I turn the temp to 82 degrees it blows cold. If I turn the temp to HI it will blow hot air.
March 22, 2016
  Followup from the Pelican Staff: Sounds like an issue with the interior temp sensor. Have you checked the vehicle for fault codes? - Nick at Pelican Parts  
Ed Comments: Thank you I did get it out
March 1, 2016
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Ed Comments: my 2000 S500 duo valve does not chick when the car is running and I unplug & plug the wire back in, so how do you get the whole unit out.
thank you.
February 18, 2016
  Followup from the Pelican Staff: It should be mounted right before the heater intake. Remove the hoses and fasteners, then the valve.
We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
SoCal E320 Comments: SoCal E320 Comments:
Hi Nick, Thanks for the advise. I will check this weekend and post the the results since i'm a weekend warrior. Thanks a bunch for your prompt reply and advise.
January 7, 2016
  Followup from the Pelican Staff: Thanks for the follow up, let us know what you find. We appreciate it.
- Nick at Pelican Parts  

Hi Nick, sorry for the late reply. I finally had a free weekend to try your suggestions. Both hoses are sending hot coolant tooth heater core. Any suggestions as what I should look for next? Much appreciated.

On a side note, is it ok to remove the two brass pins in figure 4 from the duo valves? Will the bypass create major problems?

Also, I come to find out that the last person that worked on the car put liquid gasket sealant in the radiator. Could that be a case of poor hot coolant circulation? Your responses are much appreciated.
February 4, 2016
  Followup from the Pelican Staff: If you have hot coolant into the core, is the coolant leaving hot as well? if so, the blend door may be malfunctioning. - Nick at Pelican Parts  
Dan Comments: Hi Nick. I seem to have exactly the same problem as CJ. When I set the AC controls to the lowest setting, I get cool air. However, when I set them at any higher temp, I get no air from the dash vents, and warm air at the windshield and floor vents. When the AC is off, I get very hot air from all vents. Any suggestions? Thanks, Dan
February 3, 2016
  Followup from the Pelican Staff: Me reply:

Sounds to me like a problem with an input or control. Use a scan tool to check evap and heater temp desired verse actual. - Nick at Pelican Parts
 
CJ Comments: Hi Nick,

I have 2006 CLK350 Cabrio. Climate temperature control works normally when the roof is down. Then when the roof is up it only blows 3 temperatures but no faults are showing up on diagnostics:

1 AC button on, set to 18 degrees COLD AIRCONDITIONED AIR
2 AC button off, set to 18 degrees, NATURAL AIR
3 Any temperature setting above 18 degrees RED HOT AIR regardless of whether AC is on or off.

Is this likely to be a climate sensor malfunction? If so which sensor is disabled when the roof is down so I know what to replace?

Thanks, CJ
February 2, 2016
  Followup from the Pelican Staff: Sounds to me like a problem with an input or control. Use a scan tool to check evap and heater temp desired verse actual. - Nick at Pelican Parts  
SoCal E320 Comments:
Hi Nick, Thanks for the advise. I will check this weekend and post the the results since i'm a weekend warrior. Thanks a bunch for your prompt reply and advise.
January 7, 2016
  Followup from the Pelican Staff: Thanks for the follow up, let us know what you find. We appreciate it.
- Nick at Pelican Parts
 
SoCal E320 Comments: Comments: Hi, I have a 2000 E320 w210. The Heater is blowing cold air. I have cleaned the duo valves and the problem still persists. Do you have any suggestions as to what could be the issue? Thank you in advance
January 3, 2016
Followup from the Pelican Staff: is there hot coolant flowing tot he hose at the heater core inlet? - Nick at Pelican Parts

Hi Nick, Thanks for the prompt reply. Yes the hose is hot. I just noticed something new. The car has dual climate control. The vents on driver side blow cold and the vents on passenger side blow warm not hot after the car temperature passes 80C. Just thought I share this with you. Your comments are much appreciated. Thank you in advance.
January 5, 2016
  Followup from the Pelican Staff: You may have one half of the heater control valve that is faulty. COnfirm both valves are sending hot coolant to the heater core. - Nick at Pelican Parts  
SoCal E320 Comments: Hi, I have a 2000 E320 w210. The Heater is blowing cold air. I have cleaned the duo valves and the problem still persists. Do you have any suggestions as to what could be the issue? Thank you in advance
January 3, 2016
  Followup from the Pelican Staff: is there hot coolant flowing tot he hose at the heater core inlet? - Nick at Pelican Parts  
DonO Comments: I have a 2000 e320 4-matic. When the heat temp is on HI we get hot air, if we move it down even 1 degree, we get cold air. What could be going on?
January 2, 2016
  Followup from the Pelican Staff: Faulty heater control valve or HVAC temp sensor, blend door. - Nick at Pelican Parts  
verb Comments: I have a 2000 Mercedes S500 the car is nice and warm when driving but when at a stop light it starts to blow cold air.
what should i be looking for first?
November 20, 2015
  Followup from the Pelican Staff: Check for a restricted heater core or poor flow from the water pump to the heater core. - Nick at Pelican Parts  
petlin Comments: Excellent, although my duo-valve is a bit different 1990 W124,the article lead me in the right direction. All electrical checked out and then saw one valve would shoot out and not the other. A bit of coaxing to free the stuck one and works like new!!!
July 1, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
CK Comments: I've a W210 E200K 2001 Model currently facing passenger's side blowing cold air while driver's side blowing warm air. It's been almost a year I'm trying to fix this issue.

The problem came in right after a flood. My car's carpet was all wet. and I started to have this air-con problem, one side cold one side warm.

1st diagnosed been done at workshop that I used to go.
The man told me Compressor, Condensor, Dryer, Blower, some hoses have to change. I've decided to change everything. Which cost me around $2000.

After 1 month, the problem came again. Same thing, driver'side warm, passenger's side cold.
I've sent to the workshop again, the man told me there is some hoses did not seal it properly. So he did it for free and refilled the R134a gas also.

Driving for 5 months without any issue. But now, the problem come again. I'm so frustrated with this air-con problem. Anyone can help me out with the issue? I've been looking on internet regarding this issue of W210. But it seen like a lot of different story. Will a PSE Pump affect air-con? Please kindly help me out. Appreciate.
June 9, 2015
  Followup from the Pelican Staff: First check the charge level, if low you will have what you describe. If it is low, you have a leak.

If charge is correct, check blend and mode door operation using a Mercedes-Benz scan tool. - Nick at Pelican Parts
 
Dralloc Comments: I have a 97 E320 with 107,000 miles on it. Great car in generally everything is in order. The car did not come with the owner's manual. I now the car has auto climate control with the center dash black sensor on top. Generally, how does the auto feature work? Do I need to do any pre-sets to get it to work as Im using the climate control manually. thanks.
April 29, 2015
  Followup from the Pelican Staff: Place it in auto, then adjust the temp as needed. The vehicle will do it's best to maintain the temp you select.

On a side note, check the BMW website, they may have a digital owner's manual you can download.- Nick at Pelican Parts
 
steve Comments: for MB W210

http://www.pelicanparts.com/techarticles/Mercedes-Benz/19-WATER-Cleaning_Heater_Control_Valve/19-WATER-Cleaning_Heater_Control_Valve.htm

Replace duovalve starts in Figure 7, but ends with Figure 9. Where is remainder of replace procedure?
April 18, 2015
  Followup from the Pelican Staff: Thanks for catching that. We appreciate it. I will have the article updated. - Nick at Pelican Parts  
washy Comments: Does the mercedes 1999 ml320 comes with the duovalve?
April 14, 2015
  Followup from the Pelican Staff: Yes, I believe so. - Nick at Pelican Parts  
makino Comments: Is it safe to drive the car with the hose disconnected and clamped? I really want to be 100% sure that it is the douvalve not working on the left side, causing the warm air. Because because once the part is bought it can't be returned. How much is it right now? Some says, maybe I needed a recharge of freon.
March 28, 2015
  Followup from the Pelican Staff: No. Only test it clamped when the vehicle is stationary and for a very short amount of time. DO not drive it. - Nick at Pelican Parts  
makino Comments: Or can i simply disconnect/clamp the coolant hose? Then if both vents will blow cold air for AC then, it is conclusive that my douvalve is the problem.
March 26, 2015
  Followup from the Pelican Staff: Yes, clamp it. - Nick at Pelican Parts  
makino Comments: I have 2002 E320 sedan, half left vents blow warm air and the other half blows cold air on AC function set at 63F. I've seen comments that possible cause is the left valve of the douvalve not closing or preventing the coolant to enter. Before i purchase the douvalve, can i try to force the left plunger to block the entry of coolant by maybe putting something inside the aluminum case that will push it down? maybe a stack of clothe enough to push the spring plunger down.
March 26, 2015
  Followup from the Pelican Staff: You can clamp the hose to restrict flow. - Nick at Pelican Parts  
zg3 Comments: Thank you Nick for your comments.

Though I get the feeling you answered none of my questions. Sure the blowing air adjusts in temperature based on the sensor reading blowing cooler or warmer air inside. My question is if the inside temperature should be dead stable. In my car even though temperature is set to 21 sometimes it blows warmer air and does not stop even though the inside temperature sensor shows 24, and it continue this for the next 10,15 or 20 minutes. Also the question about pops and clicks from dual valves. Should they be totally silent or they do make these pops and clicks when working?

I have already answered myself today about the inside temperature sensor disconnecting the sensor above the rear view mirror, yes it is this sensor that the 1 position of service mode of climate control shows.

Thanks
March 7, 2015
  Followup from the Pelican Staff: The inside temp will fluctuate, as if it was steady, there would be no need for variable heat / cooling.

If you vehicle warms past the point you set it, the temp sensor may be faulty or dirty.

The heater valve are generally quite. - Nick at Pelican Parts
 
zg3 Comments: Hi there, I have 2002 E320 CDI with automatic clima control, bought it 1,5 year ago. I have been working on cooling/heating system for some time, rebuilt main blower, exchanged foulty main blower resistor, rebuilt the small water pump rest function and few other things. The inside temperature sensor with it's small blower seem to work fine. Haven't looked inside the dual valves but they seem to work.

In general everything seem to work good but often I have the feeling the inside temperature isn't stable. Set for 21 sometimes I have a feeling the air blowing is little too hot and it does not want to stop blowing a little too hot for next 10,15 or 20 minutes. Then later I feel it's abit too cold. I observe the number 1 reading in climate panel service mode and while usually it stays at 22 fo 21 set, when I feel too hot it goes to 24 and stays there. It is similar in cooling mode in hot summer days, sometimes it blows just too cold and continius to do it. The temperature just do not seem to be dead on stabel.

What is little suspicious to me the dual valves while working make the clicks and pops, I can't hear them while the motor is on but when it's off in my garage and rest function is on the clicks are clearly hearable.

My questions:
1. Should the dual valves be totally silent or they make this clicks and pops when switching?
2. Should the temperature be dead on stable inside the car or in W210 it sometimes isn't?
3. Is the temperature reading in 1. position of service mode on climate control from the inside temperature sensor above the rear view mirror or this reading comes from other sensor somewhere iside air tunels?

Sorry for long post
March 5, 2015
  Followup from the Pelican Staff: It should adjust as needed. For example, you may have it set to a temp, air temp out of the ducts will change to maintain that temp. So you may feel warmer or cooler air. - Nick at Pelican Parts  
jersegurlt Comments: Hi Nick,yes the engine oil is full. We just bought the car from a private owner about 2 weeks ago. It rides like a dream except for that noise when ac or heater is on. 133,00 miles
February 27, 2015
  Followup from the Pelican Staff: Check the a/c compressor. The pulley may be faulty. - Nick at Pelican Parts  
jersegurlt Comments: It's coming from under the hood. Sounds kinda like a lawn mower
February 26, 2015
  Followup from the Pelican Staff: Check if the engine oil is full to start. - Nick at Pelican Parts  
jersegurlt Comments: I have a 1998 E430. It makes a clicking sound only when the ac or heater is on. Not constantly though. Never while car is idling sitting at stop sign/light. Do you know what could be the problem?
February 25, 2015
  Followup from the Pelican Staff: Where is it coming from? Could be a mode door in the hvac housing or debris in the blower motor. - Nick at Pelican Parts  
cvgdrb2 Comments: I have a 2003 sprinter 2500 2.7L. I have no heat, I put in a new Heat control panel, temp gauge is running 180+, check the heater control valve & appears to be closed, but when we bypassed it, I'm still getting cold air.....Baby it cold outside and inside
February 25, 2015
  Followup from the Pelican Staff: When you checked the heater control valve, was there hot coolant getting to the heater core? - Nick at Pelican Parts  
Rocket Comments: Hello, I have a 1994 c280 A/C super cold perfect. When I turn the heat up in winter time I get the passenger side hot and driver side cold. I end up with windshield defrosting on passenger side and all foggi and cold on drivers side. Any advice? God bless.
February 17, 2015
  Followup from the Pelican Staff: Sounds like the blend door may be malfunctioning. I would check operation of the mode and blend doors. - Nick at Pelican Parts  
dave Comments: Hi
I have C230 4matic 2008 the heating works but not consistently. sometime i need to drive 10 minutes in the cold before the heating starts. what can be the problem?
February 9, 2015
  Followup from the Pelican Staff: The thermostat may be faulty. - Nick at Pelican Parts  
zafcom Comments: Hi! I have a 2007 S211 E220 CDI Classic EVO w/ dual-temp system. I had my freon recharged some months ago, and since then I have MOSTLY cold air from the 2 center vents. Normal warm/hot air from all other vents, including top, bottom, side and rear ones. I'm SURE those center vents are meant for hot air too, but no one seems able to give a straight answer.

Symptoms all with cold temp outside:
-At engine start/warm up, both center vents will gradually blow warm air, then become increasingly colder.
-Center/left side will blow slightly more air than center/right side.
-Leaving Auto mode on w/ or w/out A/C but raising both knobs to Max Temp 28°C will produce no effect: both vents still cold.
-Switching to manual Front Vents Only mode will have both vents blow warm/hot air BUT the lower portion still blows cold air as if unmixed.

My Benz dealer just made me pay for an undescribed "reset of the valve", which produced the "hot air at start" effect but nothing else. Asked 5 Benz repairers, had 5 different answers, mostly pointing towards "hey, it's normal!". I KNOW it's not, I'v sat in the car for 4 years... :-
Now I read this can be a faulty Duo-Valve really? or a flap. I don't want to go back to MB since they have "more important things to do" their words, and I do not have any diagnostic tool: what can I do?
January 27, 2015
  Followup from the Pelican Staff: Center vents send fresh air, so whatever ambient temp is. As far as I recall. - Nick at Pelican Parts  
Mash33 Comments: Hello I have a 1996 C36. Passenger side of my vents blows cold air and the driverside blows hot air. No matter which setting I use. Front Vents, windshield or feet. Any ideas?
January 23, 2015
  Followup from the Pelican Staff: Sounds like a fault with the blend or mode doors. I would check the vehicle for fault codes and run a function test on the heater box flaps. - Nick at Pelican Parts  
Martin M Comments: Hi guys, I love your articles, keep up the good work.
I have a 1990 350sdl and the heater will work fine for a while but the when doing 65mph or faster will start blowing cold air.
When I slow down or stop the heat will come back. I replaced the mono valve last year.
January 20, 2015
  Followup from the Pelican Staff: Sounds like your thermostat is faulty. I would check if the engine temp is unsteady, cooling off once it warms up. If so, replace the thermostat. - Nick at Pelican Parts  
Phil W Comments: My 1992 300sl only blows cold air. I have tried disconnecting the duo valve and it still blows cold, any ideas please.
January 12, 2015
  Followup from the Pelican Staff: Is there hot coolant flowing to the heater core? - Nick at Pelican Parts  
Richard Comments: Hi Nick, Re: 2006 E320, The noise is related to whether the heater is turned on or not, and the sound seems to be coming from somewhere under the dash. The noise sounds awful, so turning off the heat, using the "off" button, stops it immediately. If I leave it on, it seems to go away within about 3-4 min. Once the engine has warmed up, I can turn the heat on "auto" button and there is no noise. Thanks for the quick response!
January 11, 2015
  Followup from the Pelican Staff: This noise could be a faulty blower motor or debris in the blower motor. - Nick at Pelican Parts  
Richard Comments: I have a 2006 E320. In the winter, when the heater is turned on, it seems that the fan motor makes a groaning/squeaking noise. Once the engine warms up a bit, the noise disappears. This only happens in cold weather. What can I do to fix it? Also, I'm interested in adding a block heater for easier winter starts. What do you recommend?
January 10, 2015
  Followup from the Pelican Staff: The motor for the engine fan or heater? - Nick at Pelican Parts  
Tom Comments: Can you guys please walk me through bypassing my heater core on a 1999 e-300 mercedes? from under the hood if possible. I'm not much of a mechanic. I've been told that the heater core is bad. I lose coolant in cold weather. Thank You!
January 6, 2015
  Followup from the Pelican Staff: We don't have a procedure for that. To bypass, remove the heater hoses and connect them together. - Nick at Pelican Parts  
wfaizan Comments: I have an 04 clk 320. The top vents, the sides and the ones in the middle never blow hot air. The vent that goes to the feet blows hot air. How do I fix this?
December 21, 2014
  Followup from the Pelican Staff: I believe the middle vents should not. The others should. First check that the knob is not on fresh air, if so, they will not supply heat. If the knob is in the correct position, check the vehicle for fault codes and check operation of the blend and mode doors using s Mercedes-Benz scan tool. - Nick at Pelican Parts  
Travis Comments: I get no air from centre front vents. Allways blowing at the sides and defrost regardless of the settings.
December 3, 2014
  Followup from the Pelican Staff: Depending on the model, the center vents are for fresh air only. - Nick at Pelican Parts  
big dawg Comments: 1993 300 SE new to me. Car had not been used but about 1200 miles per year last 5 years. Total mileage 74,000
Heat works in the front for driver and passenger but blows cold in the back seat
Any thoughts
December 2, 2014
  Followup from the Pelican Staff: Could be the heat control valve for the rear heat. I would first check if there is adequate heat getting to the hoses. - Nick at Pelican Parts  
adele Comments: Frustrated Canadian: My mercedes dealership is scratching their head and I'm hoping to get some info to direct them. Description of symptoms in 2007 Mercedes S550:
- heat temperature is lower than it used to be
- heat blows less strongly our front sides, and minimally out front centre
- symptoms improve mildly when put on manual HI but poorly when using
auto temperature settings
- front defrost works fine air wise but low heat temperature also
- engine temperature consistent during driving, etc at 70 degrees celsius

Mercedes replaced HVAC blower with no improvement in symptoms. they are wanting to now replace thermostat.

I've read through these posts but there seems to be many variances on this problem. Any ideas/direction would be greatly appreciated than you!
- Adele
December 1, 2014
  Followup from the Pelican Staff: I would check operation of the engine thermostat, that is a good starting point. Then check if the heater control valve is sending hot coolant to the heater core when the problem is present. - Nick at Pelican Parts  
Maciej Michael Comments: I have a 99 CLK 320 and i only get heat when i rev up the engine or driving,,but when i stop it stops blowing hot air. Warm but not hot. I replaced the thermostat and the main water pump. Next im thinking aux water pump or the duovalve..any suggestions what it might be?
November 29, 2014
  Followup from the Pelican Staff: Aux water pump sounds likely, unless there is a resrtiction, slowing the flow of coolant down. - Nick at Pelican Parts  
eagle670 Comments: The air flow selector switch has stopped working. I now have air blowing through the dash vents and defroster, but nothing through the floor vents. Nothing changes when turning the switch. What should I check?
November 21, 2014
  Followup from the Pelican Staff: What is the year and model of the vehicle?
The cable could be detached. Or could be electronic. Depending on what type of system you have.. - Nick at Pelican Parts
 
Don Comments: Where would the flap motor and the heater control valve located and how would I figure out which one would be the problem?
November 13, 2014
  Followup from the Pelican Staff: The flap motor or actuator is located on the hvac housing. You will need a Mercedes-benz scan tool to actuate and test it. The heater control valve is located on the engine compartment. Look for the heater hoses and follow then to it. You can check if it is allowing hot coolant to flow to the heater core. - Nick at Pelican Parts  
Don Comments: I have a 2003 E 500 and its blowing cold air with the dual climate control at the highest temp what would cause this?
November 13, 2014
  Followup from the Pelican Staff: You could have a faulty flap motor or heater control valve. - Nick at Pelican Parts  
neal Comments: i have 1999 e 320 awd HI i just had coolant leaking and the local guy said my radiator is leaking coolant and asked me to replace it and i did but soon after that my ac system is malfunctioned it was initially controls were working reversed when high it was low and when low it was high.
when i restarted the car it was back to normal, now my ac is working fine but heater fro m central console is not blowing air if its on heat mode and if its on cold mode its working fine. also the side vents are working fine.
November 7, 2014
  Followup from the Pelican Staff: I would think the repair is unrelated to your current issue. You didn't mention what vehicle you have, some models only have ambient air through the center vents. - Nick at Pelican Parts  
neal Comments: HI i just had coolant leaking and the local guy said my radiator is leaking coolant and asked me to replace it and i did but soon after that my ac system is malfunctioned it was initially controls were working reversed when high it was low and when low it was high.
when i restarted the car it was back to normal, now my ac is working fine but heater fro m central console is not blowing air if its on heat mode and if its on cold mode its working fine. also the side vents are working fine.

November 7, 2014
  Followup from the Pelican Staff: I would think the repair is unrelated to your current issue. You didn't mention what vehicle you have, some models only have ambient air through the center vents. - Nick at Pelican Parts  
Larry Comments: These were taken off the climate control panel I understand they are as follows:
01 The in-car temperature sensor. -
02 The bumper temperature sensor. -
03 The temperature of the left side heater core. -
04 The temperature of the right side heater core. -
05 The temperature at the evaporator sensor. -
06 The engine coolant temperature. –
07 The barometric pressure of the Freon. –
08 The Freon temperature. –

Regards Larry


November 6, 2014
  Followup from the Pelican Staff: Those are not helpful for me, as I don't use those functions. I would need a/c system pressure, as described earlier. - Nick at Pelican Parts  
Larry Comments: Thanks Nick for your feedback, the following are the sensor values for my airconditioner Ref: 2nd November 2014 CLK 430
1, = 19
2. = 39
3. = 12
4. = 17
5. = 18
6. = 93
7. - 13
8. = 52
not sure what they should be reading, I also checked for sensor faults , none were present.
Regards Larry
November 2, 2014
  Followup from the Pelican Staff: I need low and high side pressure from a mechanical gauge. If this from a scan tool and what sensor were you reading? - Nick at Pelican Parts  
Larry Comments: I have a CLK 430 2001, operating a/c at maximum cold both sides , checked with temperature gauge indicates right side is 9 degree C higher than the left which is nice and cold. Any ideas of the probable cause. Regards Larry

Note Right hand drive model
November 2, 2014
  Followup from the Pelican Staff: Could be a low charge or a blend door issue. Start by checking system pressure. - Nick at Pelican Parts  
Time320 Comments: I have a 1997 E320. The heat and air control has a very wide variance. In order to change the inside temperature either up or down I must change the temperature up or down by several degrees 4 to 8 degrees, then wait for minutes before a change actually occurs. Any idea what is wrong? A change of say, 1 or 2 degrees has no impact.
October 28, 2014
  Followup from the Pelican Staff: Is this an automatic climate control? If so the temperature sensor could be faulty. - Nick at Pelican Parts  
Nassir Comments: A/C Mercedes E-Class back seat for passenger not cool with the temp low of the switch
October 25, 2014
  Followup from the Pelican Staff: Are you saying the seat doesn't cool when you have it on full cold? Does the opposite side seat work normally? - Nick at Pelican Parts  
benzomat Comments: where is the ambient temperature sensor?
October 20, 2014
  Followup from the Pelican Staff: If I remember correctly, in the left front bumper, behind the grill. - Nick at Pelican Parts  
benzomat Comments: My 1999 e320 wagon outside temperature increases as the engine warms up. Consequently, when it is reading higher than cabinet temperature, the AC kicks in, even in winter. Any thoughts?
October 11, 2014
  Followup from the Pelican Staff: The ambient sensor may be asking contact with the radiator or engine. I would check it out. - Nick at Pelican Parts  
Hamkha1 Comments: Hey I have a 01 e320 4matic and I've been having one issue since I bought the car a few weeks ago. The center cent barely blow any air cold or warm a while the two side vents by the door blow air correctly.

Thanks
October 8, 2014
  Followup from the Pelican Staff: Check your owner's manual. This may be normal. Some models only draw fresh air through the center vents, - Nick at Pelican Parts  
andy_1100 Comments: Hi, I have a question on the proper operation of the heater duo valve, I have a 1995 C280, I have no issues with the heater blowing hot or cold air, it seems to work OK.
I noticed sometimes that , the heater valve is cycling and produces a knocking sound every 5-7 sec consistent intervals. I haven't found yet if it depend on the temperature setting on the climate control unit.
I've taken the valve apart, it looks clean inside, both coils show 16.9-17.0 Omh resistance.
Is it normal for the heater valve to do that?
October 3, 2014
  Followup from the Pelican Staff: The valve should not be noisy, the solenoid may be failing. - Nick at Pelican Parts  
Keith Comments: I have a 2005 E55 cold air blows in rear seat until car is warmed up and then will only blow hot air regardless of control setting. Any suggestions ?
September 14, 2014
  Followup from the Pelican Staff: Sounds like a motor flap / blend door issue. I would check operation using a mercedes-benz scan tool. - Nick at Pelican Parts  
Javedosman Comments: My E200 Kompressor 2002 starts the radiator fan after few minutes of driving and it would not go off. this in turn switches off my AC and hot air starts blowing into the cabin. the fan goes OFF after few seconds of switching off the car. it is very irritating. what could be the problem?
August 27, 2014
  Followup from the Pelican Staff: Likely a faulty fan or coolant temp sensor. I would start by checking the DME for fault codes. If the system is not working properly, a fault code will be set. This will be your best bet when diagnosing.
- Nick at Pelican Parts
 
Dick Comments: My 02 E320 blows ice cold from 2 right side vents, warm air from 2 left vents. The left heater core sensor reads 71, the right reads 57. Refrigerant reads 12. I opened the duo- valve and it was very clean and pistons seemed to move freely. Any thoughts?
August 24, 2014
  Followup from the Pelican Staff: Did you check a/c system pressure? A low charge will cause the refrigerant in the evaporator to warm by the time it reaches the left side. - Nick at Pelican Parts  
Dranoel Comments: Follow-up on 1996 C280 from August 8, 2014. Put blower on low. Changed vent positions. No clicking or grinding. Always blows out center for 2 minutes, then out to windowshield and not center. The side vents always blow.
August 12, 2014
  Followup from the Pelican Staff: You may have a faulty actuator. You are going to have to gain access and check to see if they are being commanded to move or moving without input. - Nick at Pelican Parts  
Dralloc2011 Comments: sorry I forgot to mention i have a 97 E 320.
August 10, 2014
  Followup from the Pelican Staff: Got it. Thanks - Nick at Pelican Parts  
Dralloc2011 Comments: When I operate my dual climate control system, both sides do the same thing: only blows cold air even when one side is set to the highest temp setting. Is it possible that both pintle valves could be stuck opened? Or would it be more like the scenario you answered on with Wenzel1220 with the 97 E 420 where you recommended he disconnect and I guess re-connect the 3-pin electrical connector to see if both lines run hot.
August 10, 2014
  Followup from the Pelican Staff: Yes, try unplugging he duo-valves and seeing if the heater hoses warm up. - Nick at Pelican Parts  
Dranoel Comments: 1996 C280. The A/C runs fine for two minutes then changes to put out the A/C to the window but not the center, still does the side vents. Causes the window to fog up. Hope you can help me. Thanks.
August 8, 2014
  Followup from the Pelican Staff: You may have a faulty mode door actuator. Put the blower on low, then try to change vent position. Can you hear a clicking or grinding noise? - Nick at Pelican Parts  
mikemass Comments: 99 E300. AC was blowing hot or ambient temp. Refrigerant level was good, no leaks. The Compressor clutch came on, but wouldn't create pressure. So I replaced the compressor, expansion valve & receiver drier. Checked duo valve. It is working fine. But now Pass side blows 48 degrees F, but not the driver's side. What is next step?
August 5, 2014
  Followup from the Pelican Staff: Sounds like a low refrigerant charge. I would double check the weight of the refrigerant in the system. - Nick at Pelican Parts  
kenny Comments: 1999 e300 diesel. I have hot air blow in the driver side in a/c mode. I increased drive side to 95 degree heat, then reset to 72 degree. It was back to normal. Please help. Thank you.
July 3, 2014
  Followup from the Pelican Staff: Could be a blend door issue or the heater control valve. I would check operation of both. - Nick at Pelican Parts  
Mike Comments: I have a 1999 E300TD. Sporadically getting heat from passeger vent when AC on. Can't seem to control temp of passenger side. ANy suggestions?
June 16, 2014
  Followup from the Pelican Staff: Could be a mode door or heater control valve issue. I would start by check for fault codes and the operation of the heater control valve. - Nick at Pelican Parts  
redman Comments: hi I have a 94sl 320 and when I have ac on the side and the defrost blow out cold but center does not blow anything what do think that can be? ty
June 10, 2014
  Followup from the Pelican Staff: Is the center vent turned off? Try the vent switch. - Nick at Pelican Parts  
Chuck Comments: I have e320 1997 . The driver side vent blow warm air it take a while to blow the cold.the passenger side blow cold air.what do I do to fix this.
Thank you
June 9, 2014
  Followup from the Pelican Staff: This could be a low refrigerant charge. I would check A/C system pressure. - Nick at Pelican Parts  
D Comments: Hello, I have a 1999 SLK Kompressor. And the air works. But sometimes the right side blows heat and the left blows cold.. I want them both to blow cold! And most of the time I can turn the car off and restart it and its fine.. But what do I need to do to fix this issue?
May 22, 2014
  Followup from the Pelican Staff: That sounds like a low refrigerant charge. I would evacuate the refrigerant and leak test the system. - Nick at Pelican Parts  
TL5150 Comments: I have 1994 Mercedes C280 In Winter Hot Air blows out only Driver side Vent - Cold Air out Center and Passenger Vent. In Summer Cold Air Out Drivers Side or Center can't remember and Hot Air out Passenger Vent. Is it Duo-Valve here or the entire Climate Control or Vacuum lines
April 15, 2014
  Followup from the Pelican Staff: If you are getting hot air, the duo-valve is likely working. You may have a blend / mode door issue. - Nick at Pelican Parts  
Will Comments: Hi, I have a 1997 C180. How can I prevent air coming into the system when replacing the duo valve?
April 4, 2014
  Followup from the Pelican Staff: hard not to, you have to open the hoses, coolant will leak out allowing air to enter. - Nick at Pelican Parts  
Clk430 Comments: I have a clk 430 1999 . I am getting warm air from left and right side vents. Cold from center vents . Coolant was just recharged at dealership so it's got freon. Any ideas?
March 26, 2014
  Followup from the Pelican Staff: Sounds like a low refrigerant level. I would double check it. - Nick at Pelican Parts  
Janis Comments: Can anyone guide me through the process of bypassing the heater system on my 98 ML320? I live in Florida so I don't need the heater. Otherwise I have charged the system, the compressor works but all I get is hot air.
March 26, 2014
  Followup from the Pelican Staff: You can disconnect the heater core, then connect the two hoses together. That is maybe the easiest way. - Nick at Pelican Parts  
1998w210 Comments: Hello dear,
this is Jan,i have elegance e280 and im working in saudi arabia the tempreture here reach 55 , all people here closing the heater to get extra cool, so could you please give a way to dismantle hot water,by the way,only one valve working and the other one is faulty
March 5, 2014
  Followup from the Pelican Staff: You will have to replace the fault control valve. - Nick at Pelican Parts  
WALT Comments: LIKE THE SITE
February 27, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
daveo Comments: Thanks Nick....the valve is clean and no debris. clamps still do not want to grab the valve and hold it securely. Do I need to apply more pressure to the two parts so they will clamp properly? Hard to get under it and grab it. Thanks for your assistance.
February 26, 2014
  Followup from the Pelican Staff: Something may be damaged. At this point, can you pull it out and see if you can get it assembled outside of the vehicle? This may help you see what you are doing wrong. - Nick at Pelican Parts  
daveo Comments: The clamp on one side does not seem to want to grab the bottom of the valve to hold it secure and the leaking results. how hard can i push the duo valve down? do i need a new bottom portion that has the clamps on it? thanks.
February 21, 2014
  Followup from the Pelican Staff: Check that nothing is jammed inside, debris etc. Once you are sure it is clean, lubricate the O-rings with clean engine coolant and try to install the connection. - Nick at Pelican Parts  
Daveo Comments: Had cool air on passenger side and warmer air on driver side. Removed duo valve and all looked in very good condition. Replace but antifreeze keeps leaking out somewhere on lower duo valve. Cannot see it. Could the clamps on either side not clamping it tightly? How do I know?
February 21, 2014
  Followup from the Pelican Staff: I answered you in your other thread. - Nick at Pelican Parts  
freeno Comments: hi l have a 2005 sprinter heater works on drivers side but cold on passenger side any idea what the prob could be wife is not happy, l am but there again l am driving so l am warm
February 17, 2014
  Followup from the Pelican Staff: If you are getting sufficient heat on one side, there is likely a blend of mode door problem. Might want to start by checking the vehicle for fault codes.- Nick at Pelican Parts  
Keith Comments: I have a 2009 C230 4matic. Neither the heating system or AC is coming on.I turned it up as high as it will go and nothing coming on. The heated seats work fine.
February 7, 2014
  Followup from the Pelican Staff: Check to see if the blower motor is getting power and ground when you command it ON. If it is and doesn't run, the blower motor is faulty. - Nick at Pelican Parts  
gerti Comments: there are a lot of fault codes :227 231 232 235 416417 418 459 423 424,
February 2, 2014
  Followup from the Pelican Staff: Can you supply code descriptions to save me the time of looking them up? - Nick at Pelican Parts  
gerti Comments: hello,i have a e250 98 and one side of clima blows hot and one side blows cold even if the two sides are at high temp. thanks
January 18, 2014
  Followup from the Pelican Staff: This could be low coolant or a blend door problem. Can you check the vehicle for fault codes? - Nick at Pelican Parts  
dave Comments: Just bought a 96 320e heater blows cold air both sides could I unplug duo valve to make the trip home as I have no tools with me?
January 16, 2014
  Followup from the Pelican Staff: I don't think unplugging it will restore heat. You have to figure out if it is faulty or not. - Nick at Pelican Parts  
oldfixit Comments: On a 2003 C320 4matic, where are the duo-valves located? I can only locate one valve attached to a radiator hose and it is located in front of the radiator reservoir on the passenger side of the car.
January 8, 2014
  Followup from the Pelican Staff: I believe it is located under the wiper cowl, where the heater hoses enter the firewall. Under the wiper motor. - Nick at Pelican Parts  
donniethec Comments: My 03 has a cycling sound for a couple of minutes then stops, everything seems to work fine. Only happens on start up, I can see from the right side with close out removed where you change the interal a1ir filters a steel rod and plastic belcrank moving behind the radio. Whats goi1ng on?
?
December 18, 2013
  Followup from the Pelican Staff: That could be the blend / fresh air doors moving. If something isn't malfunctioning, this is likely normal.. - Nick at Pelican Parts  
Brian Comments: I have a '99 e300 td and I have no heat. The climate control is stuck on auto and I can't change the temp. Stuck on low. I can't change to defrost nor any other selection other than vent. Basically unsafe to drive. Please help
December 13, 2013
  Followup from the Pelican Staff: I would start by scanning the vehicle for fault codes. The system is complex and a fault code will direct you to the problem area. - Nick at Pelican Parts  
jaybird Comments: no heat, no coolant getting to either side of the mono valve 1994 e420??
December 10, 2013
  Followup from the Pelican Staff: The hoses to the mono-valve are cold? If so, there must be a coolant flow problem. Check the thermostat and water pump. - Nick at Pelican Parts  
vuman1 Comments: Looking closely at a picture of a dual heater valve, I can now tell the part attached to the two 1/2 hoses should be stationary and not removed surely not sawed off. That part does not come with the new heater valve. I should have waited to have a new dual valve before removing the old one. Do you have any suggestions to fix this problem now? Thanks again.
December 1, 2013
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
vuman888 Comments: I forgot to attach the picture.
December 1, 2013
  Followup from the Pelican Staff: Ok thanks. - Nick at Pelican Parts  
vuman1 Comments: Thanks for posting picture on how to rebuilt the heater dual valve. I have a '96 E320 that has a bad dual valve, which I am trying to replace. I have removed the large water hose that has a C clamp. However, I cannot remove the permanent clamps on the two 1/2 hoses on the other side of the valve. I tried to saw off the spout on one of the valves, but the end of the spout is now stuck in the mouth of the hose. Could you please tell me how to remove the permanent clamps? Thanks a million!
December 1, 2013
  Followup from the Pelican Staff: Following your posts here. - Nick at Pelican Parts  
Shawnkirkland62930 Comments: I have a 1995 Mercedes c220. Has cold air in the summer but no heat in the winter. Trying to find out the name of the pump located under the air breather box.
November 19, 2013
  Followup from the Pelican Staff: You could have a bad du-valve or conjtrol unit. I would check if the duo-valve is operating properly, as that is the most common to fail. - Nick at Pelican Parts  
Don Comments: I have a 1998 CLK320 and the A/C appears to work fine. The heat works, but anytime I turn the heat on when not using the climate control I get the smell of coolant and the windshield fogs up badly. Is this a bad heater coil or something else?
November 19, 2013
  Followup from the Pelican Staff: This sounds like a leaking heater core to me. I would pressure test the cooling system and see if there is any coolant coming out the heater box drain, or onto the floor on the vehicle interior. - Nick at Pelican Parts  
wenzel1220 Comments: Hello Again,

so I went ahead and pulled apart the duo valve in my 97 E420, and cleaned all the odds and ends as indicated in this DIY and as well a few others ive read. what i found during this procedure was that the rubber gasket on the left valve that held the back end of the metal rod in, just above where the plunger end goes into, was shredded on both insides and out. I went ahead and trimmed what i could of the loose pieces and refitted it back into place. while reassembling the duovalve back together, i snapped just the very tip of the left plunger as well while trying to refit the housing on top of them, maybe the length of less then an 8th of an inch. Seems it wasnt in issue since after tightening everything up and adding more antifreeze to the coolant tank, my heater started working again! My question is if possible, where can i buy a new plunger and rubber gasket? or do i need to buy a whole new duovalve? Hopefully it will keep working for the time being, yet, would like to swap these two parts out since their inevitably going to fail sooner or later
November 11, 2013
  Followup from the Pelican Staff: You probably have to buy a whole duo-valve but you can buy gasket material and cut one yourself? - Kerry at Pelican Parts  
manny Comments: rear blower blows cold air all the time.hot air blows in front but rear stays cold.what could be the problem
November 9, 2013
  Followup from the Pelican Staff: The rear heater control valve or auxiliary coolant pump. - Kerry at Pelican Parts  
russ Comments: I have a 2003 E500. No heat at all, it only blows cold air. Do you think it could be the duovalve or possibly the heater control valve? The air conditioner works fine.
October 28, 2013
  Followup from the Pelican Staff: Yes or the auxiliary coolant pump. Elecrrically unplugging the duovalve should open it up all the way for full heat. Check if all three hoses are getting hot. - Kerry at Pelican Parts  
OnTheRoad Comments: 1996 e300. Only the passenger side blows correct temp. The drivers side blows cold when the heat is on and hot when the ac is on. Sounds like the duo valve. Also, I can hear the fluid moving behind the dash around when I start or stop. Thoughts? Thanks.
October 21, 2013
  Followup from the Pelican Staff: Sounds like you have air in the system. Also your heater control valve may be stuck closed, check that also - Kerry at Pelican Parts  
wenzel1220 Comments: While the engine is running correct? also, i only see 2 lines hoses running from the duo valve.
October 10, 2013
  Followup from the Pelican Staff: A "Duovalve" (meaning two) is for dual climate control systems one for the driver and the other for the passenger. You either have a single zone system (only one temperature control) and you are looking at your Monovalve (same principle, unplug it and it should go to full heat) or you have a dual zone system and are looking at your auxiliary coolant pump. Do you have a repair manual for this vehicle you can refer to? - Kerry at Pelican Parts  
Wenzel1220 Comments: I have a 1997 E 420. Today when I put on the heater, first time since I've purchased the vehicle by the way, the drivers side vents would blow out warm air yet the passenger side wouldn't. It would blow out cold air even at "HI" temp setting. Same for the rear vents in the back seat. Is this caused by the duo valve malfunctioning as well?
October 9, 2013
  Followup from the Pelican Staff: Yess it is very possible. Try unplugging the three pin electrical connector on the Duovalve and see if all three lines get hot - Kerry at Pelican Parts  
Emmy Comments: what are the proceedures for turning on my aircondion of 1997 model of E55.In addition,one part of the car aircondition blows air while the other part is cold.What is the challenge?E
September 29, 2013
  Followup from the Pelican Staff: If you have a climate control system (automatic) the the AC will come on when you have selected a cold temperature automatically. If you push the ECON button you will shut off the compressor and you will just have air blowing. Sounds like you have a dual zone system and one of the temperature blend doors may not be working. - Kerry at Pelican Parts  
Mike M Comments: Little bit confused here. There is talk of blocking pipe and by-passing. What is the difference? What do I do to totally eliminate the heating function? Do I simply block the pipe or do I by-pass?
September 19, 2013
  Followup from the Pelican Staff: It does not matter is you aliminating your heating system if you block it or run a loop back. - Kerry at Pelican Parts  
mikinzla Comments: I have: no heat at all, and only one speed with the fan,slow.
September 12, 2013
  Followup from the Pelican Staff: You probably have a bad blower module and duo valve is probably stuck closed - Kerry at Pelican Parts  
Venn Comments: I've got a Mercedes SLK 230 1998. The heater only blows out hot air. I've taken out the Duovalve and tested to see if it works when applying an external voltage to it and both solenoids work, but when connected to the car it doesnt work. any ideas? also connected an voltmeter to the cables and they seem to work fine
September 5, 2013
  Followup from the Pelican Staff: If you manually activate the valve when connected to the vehciel, does the valve close? I would try crimping the hoses, if heat goes away, then the signal from the HVAC control unit might be faulty. It's possible it cannot handle the load of the valve. - Nick at Pelican Parts  
C280boy Comments: I have this problem when I drive or at idle the car get hot in cabin and I try to turn the ac and nothing but hot air is coming out and on the heater control the shaft is broken and I guess I can't repair it because I can't find any thing to replace it with and I can't get the metal plate off I think it's easier to just get a new one but when I get it I still need help trying to put it back in do I remove the black little rubber pieces ?
July 19, 2013
  Followup from the Pelican Staff: If I understand correctly?
Your heater control valve is falling apart internally?
If this is the case, buy a new unit now.
As a temporary measure, you can dismount the failed valve unit, and plug the hoses until the new valve arrives.

-whunter-
 
golferskierbiker Comments: A Torx T10, not a T15, fits my 1999 E430 heater control valve.

BTW, for those of us with ohmmeters, it would help to know what the nominal coil resistances are and what each connector pin goes to. Also, are any diagnostic codes associated with the valve?

The new ones cost about $300, by the way.

My particular problem seems to be that one of the valves is stuck partly open because, with the A/C on, the air coming out of the left vents is about 15 degrees warmer than on the right.

Your pictures are VERY good, by the way.
July 16, 2013
  Followup from the Pelican Staff: Coil resistance is going to vary with temperature. They are pulse-width modulated so the resistance is relatively low, below 20 ohms. Most of the time they stick open or closed mechanically so cleaning them usually fixes any symptoms - Nick at Pelican Parts  
Tony Sparks Comments: My 1994 Mercedes C220 is constantly blowing out hot air from the vents when the car is moving. The faster it moves, the more hot air comes out, would the duovalve be the problem?
Of not then what do you think it is?
May 31, 2013
  Followup from the Pelican Staff: Your symptom is typical of a damaged duovalve, and exactly where I would start any diagnosis.
- whunter
 
jmperezq Comments: Dear Pelican Staff:
Since in Puerto Rico we don't need the heater. So I have proceed to bypassed the whole heater system. I did conected the input and output hose in order to make the cycle. The only thing I have some concerns is an small water pump I saw. What is the real fuction of this pump?? Best regards,jmperezq
October 29, 2012
  Followup from the Pelican Staff: The small electric pump is for the heater, it boosts circulation - flow at idle.
roy@pelicanparts.com
 
Gabriel F. Comments: Thanks man, it helped me to fix the valve on my CLK 98
October 9, 2012
  Followup from the Pelican Staff: You are welcome.
- whunter
 
jmperezq Comments: I have found that my Double Valve Heater is defective and a new one is necessary. I proceed to bypass the valve and obviously the heater until I buy a new one.
Question: Does it right or this action can affect the air condition function???
September 14, 2012
  Followup from the Pelican Staff: If you bypass the valve, you will have maximum heat, the A/c can not overcome engine heat..
If you loop the input directly to the return hose, (bypass the heater core, that will work.

roy@pelicanparts.com

- whunter
 
Dubadaddy Comments: Ok, I have rebuilt the duo valve and put it all back together, however, I am still blowing luke warm air and no A/C from the center vents. When put on "HI" it seems to blow some warm air out of the side vents only.

This is a CA car with about 160K on it. Granted I have to check the A/C refrigerant level but still trying to get the heater working. I did rebuild the thing per this link.

http://www.peachparts.com/shopforum/showthread.php?t=242566

The coils look good with all pieces of electrical connection good.

What else could be happening? Could it be that when I trimmed the broken rubber from the upper O-ring that I am now getting a mixture of radiator fluid from one side of the duo-valve to the other? Thus needing a NEW duo-valve? Doesn't seem possible but.....how can I get heat withing the normal temperature range without going to the "HI" setting?
August 10, 2012
  Followup from the Pelican Staff: If the upper O-ring is damaged, yes there will be issues.
Have you checked control voltage and ground ?

- whunter
 

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