BigDonkey

Hi all,

My AC seems to have a mind of it's own as of late. When it works it's ice cold, the problem is that if it doesn't it normally needs a vehicle restart to work again. The fan works fine, I have replaced the AC pressure switch sensor and the blower motor resistor. What should I check next?

sundered

Not sure if this helps, but my friend's car had a similar problem. Ended up being low refrigerant. Might be worth getting it checked at a shop? They can do a proper diagnosis.

na2ub

Not cayenne specific, but worth checking / swapping the relay compressor relay. These can fail intermittently at first. Second thing to check is the refrigerant pressures (when it is working), or take it to a shop like the previous poster suggested. You can get AC pressure gauges off amazon for not too much. These will allow you to top up the refrigerant too, if needed, by yourself. Just before I bought my cayenne, 2004 with 90 k miles, the PO had just had the AC topped up due to low refrigerant. 3rd thing that could cause this would be a failing AC compressor clutch (i.e. the compressor does not turn on due to the clutch). In my experience, failure of the clutch is first noticed when its really hot out, or the AC has been running for a long time. The pressure switches (hi and lo) can stop the AC from working, but often as intended, like when your refrigerant pressure is to low due to loss over time.

theprf

Cayenne doesn't have a compressor relay or a compressor clutch. The compressor is electrical variable displacement controlled by the ECU.

BigDonkey

SOLVED:

I have checked the AC loop pressures and they were within norm. I should have searched the forums a bit better as I have stumbled upon an older thread mentioning this same exact issue that ended up being the ambient temp sensor under the glove box. I unplugged mine and the AC started blowing cold every time. I found an 'Audi' sensor on Amazon and it seems to work fine so far:



I hope this helps someone else in the future


Thread that pointed me in the right direction:
https://rennlist.com/forums/cayenne-...-sensor-3.html