beqok

I have a 2014 S with about 32,000 miles and the two zone A/C. It was about 92 degrees today. Even after driving around for about an hour the air temperature coming out of the dash vents (as measured with a 6 inch probe was only down to 50 while driving and going up to close to 60 while standing at a stoplight. The A/C was set for 70 degrees and the A/C mode was set at normal and in the auto position. The electric radiator fan is working; I can hear it come on while at the stoplights. Also, engine water and oil temperatures are normal.

In my wife's Audi A6, using the same temp probe and under similar conditions, the air temp coming out of her vents would be near 42 degrees while moving and maybe raising to 46 degrees while stopped.

What are your opinions? Is there a problem? Am I likely getting low on refrigerant?

Andy E.

There are many simple things to verify prior to assuming that the system is low on refrigerant.

1) Check your condenser (located at the front of the car next to the radiator) for debris and/or dirt. Use a strong water hose to clean if necessary.

2) In stop & go traffic scenarios, the engine rpm usually never exceeds 2000. You need at least this minimum rotation to assure that the compressor is pumping at it's minimum capacity.

3) If this is not the case, it could very well be that the recirculation flap is stuck or non-operative. In high outdoor temperatures and humidity levels, the system automatically resorts to closing the incoming fresh air and going into full-recirc mode. Manually operating the recirc button will not overide the system.

To check this operation, close the doors, windows and left dash vent. Start the car and operate the A/C. Wait 15 seconds and open the driver's side window about 3/8". Light a match and immediately extinguish it; holding the smoking match near the window opening. If your recirculation flap is operating, the smoke will stay inside the cabin. If not, the smoke will exit the cabin through the window.

beqok

Tested it tonight and recirculate is working OK and the condenser "radiator appears mostly clear except for a number of bugs. Also, drove around and kept the RPM's higher and the outlet temp came down to about 44 as long as I kept it in recirculate, but when I put it back into normal mode the outlet temp quickly returned to 50-55 degrees.

deilenberger

Cooling capacity is normally measured as a differential temperature - ie - the difference between incoming air and outgoing air. You mentioned being in the 90's wherever you're located. If you're pulling 92F air into the AC system and the result is 50F air coming out - your system is working just fine.

There is no absolute temperature number that would be read at the outlets of the HVAC system - only the differential number.

Chances are your wife's Audi was already in recirculate mode. Try closing yours using the button on the console, and then measure the air temperature from the HVAC vent. Bet it's lots cooler.

If you have a "sport" button you might also switch to sport mode. Porsche really pushed for fuel economy in non-sport mode (including things like cutting back the output from the alternator to save energy) and it wouldn't surprise me if they cut back the AC in non-sport (ie - normal) mode.

One other thing - you mentioned hearing the electric cooling fan come on at stop lights, etc. With most modern AC systems the cooling fan runs all the time the AC is on. On the earlier 955/957 Cayenne - there were 2 fans - one dedicated to HVAC use that would come on whenever the AC system was on. Looking at the service manual it appears the 958.x trucks use a single fan. That fan should be on whenever the AC is on. It may change speed in response to the cooling system temperature, but if it's not running whenever the AC is on - the AC system will shut down at lights and when the vehicle is stationary due to high head-pressure at the input of the condenser coil. Check the fan operation.

beqok

Thanks for the insight on the A/C. Yep, the fan is working when A/C is on and turns off when the A/C is turned off but much slower than what I heard at the stoplights. I will try the sport mode tomorrow. The idea that the compresser might be programmed to not work as hard in "normal" mode sounds like a car makers response to MPG regs.

Thanks again.