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Porsche 911 Carrera Air Conditioning Maintenance and Recharge

Pelican Technical Article:

Porsche 911 Carrera Air Conditioning Maintenance and Recharge


1 hour1 hr


$25 to $750




Air conditioning pressure gauge, specialized AC equipment

Applicable Models:

Porsche 996 Carrera models (1999-05)
Porsche 997 Carrera models (2005-12)

Parts Required:

R134a recharge kit

Hot Tip:

Don't use non-134a replacement refrigerant

Performance Gain:

Better cooling during the summer months

Complementary Modification:

Replace main accessory belt

On any car, the AC system is a complicated beast. This project is not intended to be a repair manual for your AC system, but to serve more as a guide on how the system works and the maintenance involved with its upkeep.

Almost all air conditioning systems work on the theories of thermodynamics, whereby heat flows from a warmer surface to a colder one. Heat from inside the car is transferred to the cold metal fins of the evaporator. The refrigerant in the system picks up the heat from the evaporator and takes it to the compressor. The gas is then pressurized, which concentrates the heat by raising the temperature of the refrigerant gas. The gas is then sent to the condenser. The condenser cools the refrigerant and turns it back into a liquid from a gas. The liquid is then sent to the receiver-dryer, where any water vapor that may have formed in the system is removed. The receiver-dryer also acts as a storage container for unused fluid. From the receiver-dryer, the liquid flows into the expansion valve, which meters it into the evaporator located inside the car. Here the liquid absorbs heat and becomes a low-pressure gas. This evaporation, or boiling of the refrigerant, absorbs heat just like a boiling pot of water absorbs heat from the stove. As heat is absorbed, the evaporator is cooled. A fan blows air through the evaporator and into the cockpit of the car, providing the cooling effect.

The compressor pumps the refrigerant through the entire system. An electromagnetic clutch on the compressor turns the AC system on and off. In addition to cooling the car, the system also removes water vapor from the ambient air via the cooling process. It is not uncommon to find a small puddle of water underneath your car from the condensation of the air conditioning system. A thermostat control on the evaporator keeps the condensation in the evaporator from freezing and damaging the unit.

So what can be done to maintain and protect the system from deterioration? First and foremost, the air conditioning system should be operated at least once a week if the outside temperature is above 50 degrees Fahrenheit. This will circulate the refrigerant in the system and helps keep all the seals in the system from drying out. Most failures are caused by refrigerant leaking out of the system and can be prevented by making sure that the system is run frequently.

The belt that runs off of the main crankshaft operates the AC compressor. If you think that you might be having problems with your compressor, check the condition of the belt first. Turn on the system, and check to make sure that the electromagnetic clutch is engaging. If not, then you may need to replace it. Check the power connection to make sure it is live before replacing. The system also has a pressure switch located right next to the high-pressure port in the front cowl area, which will shut it off if the pressure inside the system is too high or too low. Check the pressures in the system and/or the operation of this switch if you're having A/C problems.

Refilling AC Systems

The biggest problem with AC systems is a loss of refrigerant. Luckily, the replacement and top-off of refrigerant is a relatively easy task. All 911 Carreras use R134 refrigerant, which can be purchased inexpensively at your local auto parts stores. The Carrera air conditioning system capacity is 850 grams (30 oz) of R134. In addition, the compressor needs a synthetic lubricant for proper operation. If you're filling a completely empty system, add 195 ml (6.6 ounces) of ND 8 refrigerant oil.

The kit I used to refill the car in this project is manufactured by Interdynamics (see Figure 1). Start the car outside of your garage, turn on the AC system and fan to full blast, and let the car run with the system on for about three minutes. Following the instructions included with the kit, connect a new can of refrigerant to the hose/gauge assembly. Connect the gauge assembly to the low-side port on your AC system (see Figure 2). Be sure to wear eye protection and heavy leather gloves when handling the coolant and gauge assembly--if coolant leaks out at any time, it can freeze a small patch of skin on your hands quite easily and give you frostbite.

With the car running and the AC system turned on full blast, take a reading on the pressure gauge. If your system is properly charged, it should read between 25 and 45 psi. If the pressure is low, then turn the valve on the can to release more refrigerant into the system. Be sure that you shake the can for about 30 seconds and turn it upside down when you connect it to the gauge assembly. Also be aware that the pressure gauge reading will automatically elevate as you are adding more coolant--periodically close the valve on the can to check if the pressure is rising in the system. If the pressure doesn't increase after adding one complete can, then you most likely have a major leak in your system, and you should seek the help of an AC system professional mechanic.

With the system properly filled and measured with your gauge, you should head to the passenger compartment and check the temperature of the air exiting the vents. On a system that is operating really well, the temperature will be in the mid-30s Fahrenheit. For systems that are older and weaker, the temperature readings will mostly like be higher. Also keep in mind that if your system is cooling air in the 30-degree-Fahrenheit range, the compressor on the car will tend to turn itself on and off, and the temperature will rise up and down slightly. This is not a defect of the system--the compressor turns itself off as the temperature in the evaporator nears the freezing temperature of water. This prevents the evaporator from becoming frozen and clogged with icy buildup.

Shown here is a great starter AC kit from Interdynamics.
Figure 1

Shown here is a great starter AC kit from Interdynamics. This kit contains three cans of R134a refrigerant and oil and is specifically designed to replenish older cars that may have a few small leaks in the O-rings of the air conditioning system. Included with the kit are a can adapter valve, an in-line pressure gauge, and several adapters that are not required for use with the Carrera. The kit is available for about $35 at most general automotive stores and contains everything that you need to recharge your R134a air conditioning system.

This photo shows the location and orientation of the AC ports on the 911 Carrera.
Figure 2

This photo shows the location and orientation of the AC ports on the 911 Carrera. The AC ports are normally covered with plastic covers that simply screw off (inset). The low-side (the side that you attach the gauge and refrigerant to) has the smaller port adapter and is attached to the larger pipe (yellow arrow). The high-side (used primarily for checking the compressor during diagnostic testing) has the larger adapter (green arrow) and has a smaller diameter pipe.

With the engine running and the system engaged, connect the gauge to the low-pressure port on the AC system.
Figure 3

With the engine running and the system engaged, connect the gauge to the low-pressure port on the AC system. The high side has a larger adapter, so that you can't accidentally attach the gauge to the wrong port. With the gauge attached, you can now turn the valve to add more refrigerant to the system. In the photo inset, you can see that the pressure for this AC system is exactly where it should be--in the middle of the white range. Remember to use heavy-duty leather gloves and eye protection when working around AC components--it's possible that a fitting or a valve may break or leak refrigerant on your hands.

Your hand is a pretty poor indicator of relative temperature.
Figure 4

Your hand is a pretty poor indicator of relative temperature. In order to get an accurate reading, I recommend that you use a digital thermometer, like the one shown in this photo. Final temperature performance of your AC system will vary based upon a number of factors: age, quantity of refrigerant in the system, and the condition of the compressor and associated components. This car is a 1999 Porsche with 80,000 miles on the odometer. The vent reading is 46 degrees Fahrenheit (8 degrees Celsius) with the AC at full blast. Outside temperature when this reading was taken was probably around 70 degrees Fahrenheit. You should expect at least about a 20-degree drop from the outside ambient air.

Comments and Suggestions:
Steven B Comments: Hello, Replacing condenser and dryer this weekend. System is empty due to having leaked for the past several months. I will be vacuuming to remove moisture and recharging the complete system. Does the ND 8 oil get added directly into the condenser?
January 18, 2018
Michael 997 911 Comments: Hello,

great write up, I learned more from this than any other article. I have 1 2008 997.1 C2, when the AC comes on it seems to make a cycling sound inside the car like it is compressing up and releasing and now I have some noise from the engine bay when the AC is on. With the AC off both noises are gone.
the AC runs super cold, no issues there. I dont think it is the compressor but could be the clutch perhaps? would that cause the cycling noise inside the car any ideas?
November 1, 2017
  Followup from the Pelican Staff: Can you hear the noise more under the engine hood or the interior? - Nick at Pelican Parts  
steve Comments: Is the refrigerant in the 1994 911 turbo 3.6 AC system also R134 or do these older vehicles use R12 ?
August 1, 2017
  Followup from the Pelican Staff: Type R-134A - Nick at Pelican Parts  
waltergoh Comments: The Carrera air conditioning system capacity is 850 grams 30 oz of R134

So to say i must fill to 850gram?
June 15, 2017
  Followup from the Pelican Staff: Yes, if it was emptied. - Nick at Pelican Parts  
Glenn Comments: I have a 1996 993 C4 that has a very very slow frig leak. Is there anything I can add that might fix the leak. Again it's very slow.
June 12, 2017
  Followup from the Pelican Staff: No, only way to repair is fix the leak. - Nick at Pelican Parts  
waltergoh Comments: i have 2007 911. just replace brand new evaporator and flush my whole system.
The car still have this hissing noise.
Car running cold during highway and stationery, But once car move off from stationery car make hissing sound and air con not cold. After 20sec air con cold again.
June 12, 2017
  Followup from the Pelican Staff: I would have someone locate the leak with a leak detector. - Nick at Pelican Parts  
Mitch Comments: Have an 04 turbo. Car blows really hot air when ac is on. Compressor clutch is engaging fine. Charge shows its fine. Mixing flaps all show operational when durametric cable is hooked up. Any thoughts?
May 9, 2017
  Followup from the Pelican Staff: Possible air in the system. All else sounds OK. - Nick at Pelican Parts  
jackie Comments: i have 2000 996 , when the ac on, have the water leaking in the car, can you help me to know what is wrong with the ac? thanks
April 30, 2017
  Followup from the Pelican Staff: The drain for the evaporator is plugged. You may be able to clear from below. Working under the vehicle in the area of the evaporator, look for a small rubber hose, about 1/2" diameter. The end may be pinched flat. try to clear any debris. if that doesn't work, you will have to remove evap to clean drain. - Nick at Pelican Parts  
Chris Comments: Hi I have a 997. Recently my ac started making a hissing noise and it has stopped cooling. Hissing only happens when fan is on. Will it be a simple Regis or does it sound more sinister?
Thanks in advance for any advice
March 31, 2017
  Followup from the Pelican Staff: Sounds like it has sprung a leak. Usually this hissing I've found to be from a leaking evaporator. - Casey at Pelican Parts  
Richard Comments: I have a 2003 996 c2. We recently replaced the air con compressor with an aftermarket new one. When it first went in the aircon worked when the car was stationary but not when the car was moving. When I switch the aircon on now, the engine slows but the compressor is not switching on. Any ideas please?
March 21, 2017
  Followup from the Pelican Staff: What are the high and low side pressures? - Nick at Pelican Parts  
Steve Comments: My aircon is permanently on unless I switch to eco mode. Does this mean my cabin temperature sensor needs replacing? If so, do you know where it's located? Thanks
February 20, 2017
  Followup from the Pelican Staff: That is normal operation. Later they turned ECO into AC OFF - Casey at Pelican Parts  
Bfstake Comments: Greetings- 996 carrera 01. I recently curbed the heck out of my car on the front passenger side. I bent the rim, damaged the radiator bigger picture one behind the outer smaller one. When I replaced the bigger radiator, the 1/4" tube that connects to the hoses on the smaller radiator started leaking. There was a hairline crack that I was able to weld and repair. When it leaked it leaked at a high pressure and seemed cold. It also just happened to be cold outside. However, now the ac does not blow cold. Is that smaller outer radiator related to the ac system and does freon run through it? Or is my ac issue unrelated to my embarrassing curbing incident? Thanks
December 24, 2016
  Followup from the Pelican Staff: That is the condenser line. You will have to replace it, the receiver drier and evacuate and charge the system. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
MSMMiami Comments: Hi, I had to replace one condenser. Now, when completely refilling the system, is there any type of bleed action necessary to remove any air?
December 1, 2016
  Followup from the Pelican Staff: Yes. The system has to be evacuated using an A/C service machine. The vacuum will removed air and moisture from the system before recharging. - Nick at Pelican Parts  
David Comments: 2005 997 Carrera: When I turn on the A/C the carimmediately stalls. Even when reved up it will stall. When I shut the A/C off the car runs fine. Any thoughts? Thanks
October 25, 2016
  Followup from the Pelican Staff: Compressor is likely seized. - Nick at Pelican Parts  
Brett Comments: Nice! Thanks for showing how straightforward this actually is. AC is up and running again. Here's hoping there is no major leak and it stays up.
June 15, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
Patrick Comments: can you service my 1981 928s ac system
May 29, 2016
  Followup from the Pelican Staff: Pelican can get you the parts.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
Arlandes 26 Comments: Hi Sir,
I have a 996 targa 2002.Air con is blowing cold air unless you push the temperature at the highest setting.Is the cabin temperature faulty?? and where is it in the car?
March 6, 2016
  Followup from the Pelican Staff: Could be the evap sensor, on the evaporator. have you checked what system pressure is when the problem is present and when it feels cool enough? - Nick at Pelican Parts  
Jim Luke Comments: Thanks for the reply.
I put in a good climate control unit. Everything works correct except panel mode is always on, I can only stop the airflow thru the manual vent thumb wheels. Any thoughts?
January 29, 2016
  Followup from the Pelican Staff: lowering the blower doesn't shut it off? Might be a defective panel. - Nick at Pelican Parts  
Jim Luke Comments:
Thanks for the reply. The donor control unit fixed the airflow directions but was stuck at full heat mode, temp control did nothing and the temp control servo is new and shows as good. Totally stumped, any help much appreciated.
September 23, 2015
  Followup from the Pelican Staff: Does servo get control voltage to change from cold to hot? I would confirm it is. - Nick at Pelican Parts  
Jim Luke Comments: Hi, have a strange one for the climate control system: My '00 996 had the A/C & heat temp changing from cold to warm as the car heats up, no matter what temp was selected. Airflow was always panel only no matter the direction setting floor, defrost, etc.. AUTO seems to work and fan speed will go up or down depending on the temp selection getting near or further from an ambient of approx. 70F. Checked all actuators and found servos for airflow direction located on pass side, for defrost, panel, floor and the temp control servo bad. Replaced these and nothing changed except now stuck at a very cold temp even when car warms up. I borrowed a new & functioning control unit, installed it and the changes were: All air flow directions change correctly for panel, defrost, floor, etc. The temp seems to be stuck at full heat and very hot, temp setting has no effect, fan still works correctly. I reinstalled original control unit and it’s back to a cold temp and panel mode only for airflow, All control buttons have no effect on the unit except to change fan speed, Auto off/on, A/C off/on and maybe recirc. I am stumped, any ideas?
September 14, 2015
  Followup from the Pelican Staff: Sounds to me like the donor panel fixed it. I would try to find a used good panel to replace yours with. - Nick at Pelican Parts  
Jay Comments: '01 996: the A/C cools fine but the humidity levels rise and fall significantly; also condensation builds up on the windscreen to the point I need the windshield wipers. Could it be the Dryer? Low Freon?
September 12, 2015
  Followup from the Pelican Staff: COuld be a plugged evap drain. - Nick at Pelican Parts  
Russell Comments: I stayed within pressure specs on the charge last year and this year - actually stayed on the lower side of spec this year. This newest charge only lasted 2 weeks so I assume that that hissing/leaking filler valve is the problem. Do you carry a replacement for that valve?
August 17, 2015
  Followup from the Pelican Staff: We can get you one.

I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
Russell Comments: I charged my system last summer assuming that since the car is older 2001 C4 it would just need a recharge. This spring it quit again and when charging it today I noticed that the valve in the low side filler port was hissing. I'm assuming that is the problem with the AC and the reason last years charge didn't make it a year. Does the valve itself need replacing? And, if so, how is it replaced - it doesn't look much like a Schraeder valve - so it wasn't obvious to me.
August 7, 2015
  Followup from the Pelican Staff: Sounds like you have a leak or you overcharged the system, causing the pressure relief valve to blow. I would have the system leak tested. - Nick at Pelican Parts  
qlondon Comments: hi. I recently bought a Cayman s 2006 and noticed that air con was not working. basically blowing hot air. I took it for a recharge and the mechanics told me the machine would not recharge it and indicate a leak. I took it somewhere else a shop who does air con repairs thinking it was the condenser or compressor but the guy called me back saying he could not locate the leak...I have had that car for 3 days and it's already a pain...please could someone help me with advice?
July 7, 2015
  Followup from the Pelican Staff: If there is a leak, you will have to use a refrigerant leak tester and dye to locate it. Could be in many places. If the mechanic is struggling, take it a Porsche specialist. - Nick at Pelican Parts  
RV2000 Comments: Hello,
2007 911. When I initially turn the aircon on it blows mildly cool air with the Temp setting on "Lo". If I toggle the temp setting up a few degrees then back down again to "Lo" it begins to blow cold air. What could be causing this? Is this a refrigerant issue or a hvac panel issue? Any suggestions would be appreciated. Thanks.
June 4, 2015
  Followup from the Pelican Staff: It's a good practice to start with the refrigerant. These computer controlled systems do odd things when the refrigerant level is low. I have seen: warm air distribution from half of the vehicle vents, temp sensor faults, and stepper motor potentiometer faults caused by low refrigerant levels. Clear all faults after recharging. Once you know that the system has the proper charge you can check faults in the climate control system and work through the relevant test plans. - Casey at Pelican Parts  
DV10 Comments: Hi Sir,
I have a Porsche 911 997, it is manufacturing in 2007, Recenty when I turn the aircon on, it will blow out some dust, it is a small piece of "form" we use for packing, please let me know how to do.
September 15, 2014
  Followup from the Pelican Staff: This could be the insulation for the evaporator or foam from blend door seals. - Nick at Pelican Parts  

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Page last updated: Fri 1/19/2018 02:41:55 AM