Freddy

Hi folks,

I am getting desperate about my two 911s. I own a 964 C4 Cab (40k miles) and a 993 C4 Cab (6k miles).

Both cars are giving me trouble with the air con!

When the car is running everything is fine and the car gets cool inside - I can feel the cool air going out from the dash grills. Meaning I have enough gas in it and no leaks!

As soon as I get stuck in traffic with the engine idling I fell that the cool and dry air gives space to a more humid and warm blow... pretty annoying on warm days driving at the rush hour!!

This is happening on both cars!!

How can I have this problem corrected? Is there a way to keep the air cool all the time? I would like to avoid taking both cars with the same problem to a dealer, and would rather do this service at home.

Any help would be highly appreciated!!

Cheers,

Freddy
http://www.356carrera.net/imagens/all-4.jpg

Felix

The first step is to make sure your AC condensor cooling fan is running. Look on www.pcar.com for a very good DIY on checking the operation of the AC condensor fan. And check the oil cooler fan while you're at it.

If the AC cools adequately when the car is moving that strongly points to a problem with the fan. The resistor is a known weak point.

David in LA

have you already recharged the freon? if yes and the systems only blows cold for a while then gets back to humid, then your system is probably leaking.

mike cap

Freddy,

If your A/C sytem blows cold initially (measure the temp with a temp probe in the center vent - engine above 2,000 rpm, MAX COOL mode, and RECIRC) at about 48 F to 52 F and then (30 minutes or so) gets warmer and warmer, your evaporator is icing over and not allowing any ambient air to pass through it, cool and enter the cabin. You are correct in your statement that you "have enough gas in it and no leaks" if you initally blow cold at these temps.

The evaporator is supposed to ice up enough (key word), but not too much. It ices over, but not fully, ambient air continues passing through the fins and you get the cold air in the cabin. A temp sensor on the evaporator senses the evaporator temp and shuts off the compressor at 32 F, allowing the lower "blocking" ice to melt off, open up the fins and the cycle starts over. If you have a sensitive enough temp probe in the center vent and everything's working properly, going down the road you can actually see the center vent temp change as thie compressor cycles on and off.

You have one of two problems:

1) Your evaporator drains are blocked, causing the melting ice to back up and remain frozen on the evaporator, blocking it off completely. The water can't drain off the evaporator, in other words. Simple fix of blowing out the drain area. Then the ice melts when the compressor shuts off, the water drips and the evaporator fins open up.

Check to see if you have water dripping from the evaporator drain initally when the A/C is working and then later when your A/C is blowing warm. Dripping is good. No dripping is bad.

2) More likely (since two cars are doing the same thing), you need to have the evaporator temp sensors repositioned. See my write-up to save time.....

https://rennlist.com/forums/993-forum/222097-a-c-evaporator-icing-long.html

Feel free to call me if you would like more help on this. You can spend months (I did) chasing your tail over this fairly simple problem. My office number is 315-253-9721. Ask Sharon or Laurie to track me down.

BTW, looked at your photo gallery - nice fleet !!