Budget M3

After the 2006 CTT is left in hot sun(e.g. Left parked in the sun after driving for 20+ minutes), upon the next restart the AC only operates for ~10 minutes on max AC. Then there is a "groaning sound" from the passenger side of the engine bay and the AC shuts off completely, even the fan stops. It sounds like the compressor is shutting off. The HVAC controls still display the AC temperature and the display shows max fan speed. It seems like the AC may be tripping a sensor of some type and is shutting itself down as a preventive measure because if I shut the vehicle off, even for 5 minutes, the AC starts working normally again. As long as I do not run it on max setting it seems to work OK and the problem does not recur until another "heat soak" event.

I tried a search, but came up empty. Any ideas?

Petza914

I'm no expert, but it sounds like maybe the condenser is freezing up. This usually happens when you're low on refrigerant and the system has to work too hard to try and achieve the necessary cooling. When not in Max setting, the hot ambient air temperature may be enough to keep melting the ice that's forming and keep it running. You can try a test...run it on max until it quits, then while still driving and not turning the car off, shut just the a/c off for a few minutes (eco button), then turn it back on again and see if it works. If it does, go in for a recharge and an investigation of where the refrigerant might be escaping.

Andy E.

This may also be due to a faulty blower fan. Prior to failure, the fan will squeak or groan and then suddenly shut off. After a brief cool-off period, the fan will resume operation. As petza stated, the evaporator coil can ice over once the blower fan fails to draw adequate air over. Once frozen, the system will normally shut down.

Try running your blower fan on high speed without the A/C engaged. This will determine whether or not your blower fan is the culprit.

Orantes

+1

If you have never changed out the blower fan, then this is your problem. Take the assembly out (easy), remove the motor from the shroud and have a look at the electrical bushings that drive the motor. They will be worn down to almost nothing. I previously had very similar symptoms as you have described.

The regulator / blower resistor is also known to die (big blue resistor visible above blower assembly) but the blower fan itself is the most likely culprit.

Budget M3

Thanks for the input folks. Blower fan malfunction makes sense for the symptoms I am seeing. It is original to the truck. I will check it this weekend as suggested. If I do need to remove it to check the bushings, does it come out from the top center of the engine bay near the firewall like other cars?

Orantes

No, it is under the glove box. Check out the Pelican Parts HVAC blower fan removal process.

It is very simple to get it out as a complete assembly with plastic shroud.

Most people replace the whole assembly as they are readily available as replacement part.

deilenberger

And as a hint - the VW Tourag one appears to be identical, several people have used it for a replacement, at about 1/2 the cost of one from Porsche.

Budget M3

Appreciate the additional tips, guys. Thanks

Dilberto

There is a low pressure compressor switch, just under the front wiper motor assembly that goes bad and will force ECON mode, after awhile. Note that you MUST pay close attention to how the wiper arm washers and grommets assemble....or, face a non-op wiper. OEM Porsche part #955.613.137.03 can be found on eBay. When replacing - a dab of fresh, synthetic PAG oil(Polyalkalene Glycol) around the connection 0-ring is recommended. No need to discharge R134A....

deilenberger

How does one do this without discharging the system? Is the switch not part of the coolant circuit?

Dilberto

It's a low-side pressure switch. Only hi-side(discharge) circuits require evacuation. When removing the old switch - you'll hear a quick, "pssht" as the quick-disconnect ball spring in the line prevents escaping gas.

nodoors

If it is not either of those two things it could also be the compressor clutch. When they get hot the electromagnets lose efficiency. How many miles are on the car?

deilenberger

Ah.. the quick-disconnect is what I didn't know about.

Question - maybe you'd know the answer. Is there a quick-disconnect on the connections to the compressor on the 958 systems? Reason I ask - in the manual for the 958, under replacing the compressor there is nothing about discharging the system. There is a section describing depressurizing the compressor after removal to drain and measure the amount of oil in it - leading me to believe there may be QD's used for that connection also.

If so that might explain why I saw nothing about recharging my system when my engine came out last summer. And it might explain why it was about 12oz low on R134A (going by the pressure/temperature curves in the service manual.) It was out for about a month, and I have no idea how really leak-free the QD's might be.

The manual is annoyingly vague on the subject (but does repeat every topic at least 8 times - once for each model/engine variant.)

Shawn Stanford

^This. Those were the exact symptoms I had. I replaced my fan and I haven't had a problem since. Here are a couple of threads detailing the fix. It's an hour in your driveway. I paid $85 for a Chinese fan off eBay, it's been working fine for 4 years.

https://rennlist.com/forums/porsche-...lfunction.html

https://rennlist.com/forums/porsche-...-thread-2.html