Tim Noce

Alright, so about 20 mins into my 8 hour trip to central MO for a wedding this weekend my ac stopped working (recharged and vacuumed tested it about 2 weeks ago.) the fan still blew in both the front and the back but the "AC" button did not light up. The air was hot At the coldest setting and moving the temp bar just made it hotter. After doing some research on here I found that another rennlister had a similar issue a while back. After doing some of the troubleshooting steps from that thread my "AC" light came back on! The problem is the ac still doesn't kick on and warm air still blows. Just FYI, the last troubleshooting step that fixed the problem was to change the fan setting to defrost and back again.

Any ideas?

Bertrand Daoust

The head unit relay maybe?

Here's a thread on AC diagnosis:
https://rennlist.com/forums/928-foru...diagnosis.html

Hope this will help.

69gaugeman

AC not working means what exactly?

Does the compressor clutch engage? It should be on all the time the Ac button is pressed (or defrost mode is on)

Also the heater valve may be open. This would also cause this same problem.

MainePorsche

Pull the center console carpet off on the driver's side, get a your mirror, and line up and re-attach the harness to the AC button. The harness connector is recessed in the corner there, and it is hard to see - easy to be fooled that you're plugged in. If not attached, no light at button and no current to HVAC relay.

soontobered84

Maybe it froze up and did not allow air past the coils, which would mean only warm air would circulate into the cabin.

griffiths

AC Troubleshooting Sharks

Schocki

If your ac compressor still engages but you still have hot air only I would first assume that your motor for the temperature flap is faulty.

The motor sits above your right knee when you drive the car. Try the following: turn on the ignition, but do not start the motor. Move the temperature lever on the HVAC control unit. If everything is OK you should hear a little motor running. This motor is part of the temperature servo that moves the temperature flap.
I had the same problem and it were simply defective transistors inside the servo box.
With the movement of the arm that the temperature flap is adjusted, the heater valve is turned on and off too with this movement. Meaning your servo is now at full hot AND your heater valve is always open as soon as you start your car!

If the above check is indicates a bad servo temperature box, do the following.
Remove the motor (only two screws) and disconnect the two electric plugs. As soon as the motor is removed the flap will drop to "Full cold"
Bridge pin 2 (red) and pin 3 (black/red), this will permanently close the heater valve.

Open the servo unit and clean everything, replace the four transistors inside. They are most of the time responsible for a "full hot" temperature servo box.

Temporary solution: just drive without the box until fixed and with a bridge installed. This will keep your head cool

Below a couple of pictures...

Tim Noce

Thanks for the help everyone, I'll check out a few of these this weekend. Just some clarity, because I know there is a lot of info... The AC light on the switch does light up now. It didn't when I first noticed the problem but works after messing around with some settings. Also the air is always hot but if I move the temp setting to a hotter setting, the air gets even hotter.

69gaugeman

Classic symptoms of a failed heater valve on the firewall in the engine compartment and low refrigerant.

Tim Noce

So just to follow up on this (I know it has been a while!) there was two issues at play:
1. There was a leak on the freon input valve that ended up being replaced. This is a good place to check if you are able to pressurize the system yet still have it leak out over time.
2. I ended up zip tying the heat valve (flappy valve?) open and now it works like a charm!

I guess if I drive in the Chicago winter this year that zip tie will be cut

Thanks for everyone's help!