2004 CTT 4 Zone A/C Behavior cold in front, hot in back

[deepraver]

Sounds like a mullet... LOL. Anyway.. A/C is blowing ice cold up front, hot out of the back seat console, both vents and both rear pillars. Yes I checked the front/back temp settings and I am now running it with back off and just the front set to normal and its fine. I'm in St. Petersburg, FL so its still hot here. What should I look for? DIY or see my mechanic? I do have access to a PST2, just have not had an opportunity to hook it up yet. Just wondering if anyone knows right off the top of their head or what order to start diagnostics...

 

Thanks in advance!

Andrew

[deepraver]

Bump

[JFP in PA]

Bump

 

Please do not "bump" your posts, it is against forum rules.

[RFM]

I assume it's a separate front/rear AC system, in this case there is something wrong with the rear part, a PIWIS is strongly recommended to check the several parameters, servo's, sensors, etc., without any equipment it will be hard.

[deepraver]

I stated above that I have access to a PST2 (predecessor to the PIWIS), will that not work? The PST2 is updated to 2005. My CTT is a 2004.

[Loren]

The last update to PST2 was 2004 when it was replaced by PIWIS. It will have limited tests for Cayenne.

PIWIS will have more diagnostic tests for 2004 and newer cars than PST2.

[deepraver]

I don't have access to a PIWIS. Is there really no way to diagnose this with a PST2? Going to the dealer is not an option I'm willing to undertake. Our local dealership is the worst.

[Loren]

You can try but the PST2 stopped development in early 2004 - so many of the Cayenne (and newer car's) features were not included in it.

[deepraver]

It works just fine for everything else 2004 and also has 2005 data.. I checked. I can reset my service, run diagnostics, see all the ODB codes, etc.  Has anyone ever run into this problem before. It's OK to say "I have no idea"... just looking to see if anyone has every had to diagnose this problem and what steps to take. 

[wrinkledpants]

You need to be willing to pay some money to troubleshoot.  There is nothing we can do if you're not able to get somewhere to have an actual diagnostics done.  And, I can't think of anything you could do since you need an AC hose setup to test for leaks, a Durametric to test the servos.

 

It would be unusual to have all your servo motors fail to the point that the back of the car blows warm air out of all the vents.  Without a Durametric or a trip to the dealer - there will be no way to know for sure.

 

It could be an AC system charge issue, but it usually impacts both front and back.  I'm not aware of any switch or servo in the AC refrigerant lines between the front and the back, as I believe it's an open system.  So, that leaves something wrong with your evaporator in the back, or some type of check valve.  But, again - that's going to be above and beyond the skill of any Midas tech, or what a Durametric could troubleshoot.  

[bigbuzuki]

You could always get access to the rear a/c unit and inspect the temperature control servo/flap, ensuring it is not stuck in the full heat position.