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Pelican Technical Article:

Heater Valve Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

*****

Tools:

T30 Torx socket, 13mm socket, flathead screwdriver, hose clamp pliers

Applicable Models:

Mercedes-Benz E320 (2003-09)
Mercedes-Benz E500 (2003-06)
Mercedes-Benz E55 AMG (2003-06)

Parts Required:

Heater valve, heater hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Heat will work again

Complementary Modification:

Change thermostat, flush cooling system

Mercedes-Benz W211 models are equipped with a climate control system or HVAC, which automatically controls cabin temperature once a temperature is set on the HVAC control head in the center dashboard. Left and right (passenger and driver) temperature settings are controlled separately. The system controls air-conditioning, heating, internal blower motor operation and numerous air outlets. The electronic control module governs the operations of the following components:

Heater valve in the center of the engine compartment; controls the flow of hot coolant to the heater core inside the HVAC housing underneath the center dashboard

AC compressor in the engine compartment; driven by engine accessory belt

Blower motor underneath the dashboard behind the glove compartment; motor speed modulated using the blower final stage

Front and rear air outlets; nearly a dozen electric stepper motors attached to vent flaps control the flow of fresh or recirculated cold and warm air to windshield, face-level vents, foot wells and rear compartment

Engine cooling fan; microprocessor and engine control module (ECM) determine operation and speed of cooling fan

The heater control valve controls the flow of hot coolant to the heater core. If your vehicle has no heat and the cooling system is properly bled, the valve may be faulty (stuck closed). You may also have a situation where the vehicle has heat all the time. This may be a valve that is stuck open. In this tech article, I will show you how to replace it if necessary. Aside from mechanical failure, the heating problems in your car may also be caused by a malfunction in the electronics of the climate control system. A dedicated Mercedes-Benz scan tool can read fault codes off the HVAC system. But I'll show you some simple tests of the system that you can do using a DVOM.

To do any work on the cooling system, wait until the engine has cooled off.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Drain the cooling system. See our tech article on cooling system draining and filling.

This photo shows the location of the heater control valve (red arrow).
Figure 1

This photo shows the location of the heater control valve (red arrow). It is located at the center of the firewall, below the wiper assembly. To access it, remove the wiper assembly. See our tech article on wiper assembly replacing.

With the wiper assembly removed, you will have to fold the foam shield out of the way (red arrow).
Figure 2

With the wiper assembly removed, you will have to fold the foam shield out of the way (red arrow).

Start by folding up the foam shield and placing it under the tab on the cowl (yellow arrow) to hold it in place.
Figure 3

Start by folding up the foam shield and placing it under the tab on the cowl (yellow arrow) to hold it in place. The heater valve is now exposed (red arrow).

Remove the upper engine cover.
Figure 4

Remove the upper engine cover. See our tech article on engine covers removing. Working on the engine side of the firewall, using a flathead screwdriver, lever up the wire lock (red arrow) until it stops. Then pull the heater hose input (yellow arrow) straight out to remove it.

Next, remove the upper heater hose clamp (red arrow).
Figure 5

Next, remove the upper heater hose clamp (red arrow). Use a pair of hose clamp pliers. Slide the clamp with the hose away from the heater control valve to remove it. This style of clamp requires special pliers. Standard pliers won't work.

Working on the side and top of the heater control valve, using a flathead screwdriver, lever up the wire locks (red arrows) until they stop.
Figure 6

Working on the side and top of the heater control valve, using a flathead screwdriver, lever up the wire locks (red arrows) until they stop.

Then, pull the rubber grommet out of the firewall.
Figure 7

Then, pull the rubber grommet out of the firewall. Detach it from the engine side (red arrow). Then feed it out through the wiper side of the firewall (yellow arrow).

Pull the heater valve out of (yellow arrow) the heater core connections toward the engine.
Figure 8

Pull the heater valve out of (yellow arrow) the heater core connections toward the engine. If it feels stuck, double check both wire clips are released. They usually come out with little effort. Once out, flip the valve over. Then press the release tab (red arrow) and disconnect the electrical connector by pulling it straight off.

Remove the heater valve from the vehicle.
Figure 9

Remove the heater valve from the vehicle. This photo shows the valve removed. To install the new valve, reverse the removal steps. Be sure that the wire clips are engaged. Listen for an audible click. Fill and bleed the cooling system. Once complete, double check all the hose connections and check the engine for coolant leaks.

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Comments and Suggestions:
Tangles Comments: Hi I seem to I've a similar problem, I have a heatervalve that looks like the one in your pic, except so much more difficult to get to.it has 12 volts across it weather on or off heat.
I suspect some sort of hot cold air mix flap is the problem. Would the vehicle have something like this ? W211 e320 03
June 24, 2016
  Followup from the Pelican Staff: if it always has 12 volts, the control unit is not functioning correctly. - Nick at Pelican Parts  
max964t36 Comments: I have done the replacement yesterday by following this tutorial step by step. Thanks Pelican, would never make it without your help!
November 2, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Tim Comments: I replaced the heater control valve on my 05 e320 Mercedes but the heats still doesn't work. There is voltage at heater valve connector, but the voltage doesn't change when you turned the ac switch on or off. Any suggestions
September 26, 2015
  Followup from the Pelican Staff: is there hot coolant getting to the valve? Have you checked voltage on all the wires? What are the terminal numbers and wire colors you are testing? What is the voltage on the wires? - Nick at Pelican Parts  
Tim Comments: I didn't see the test for electronic climate control system
September 16, 2015
  Followup from the Pelican Staff: Where were you looking? - Nick at Pelican Parts  

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