Having the first REALLY hot weather since the 95 Cab purchase last September. The A/C works fine when driving at medium/high speed, however when down in the below 30 MPH range it tends to weaken/cease. I just get warm air from vents. Is this standard or symptomatic of a problem? (Couldn't find anything relevant in a search.)

Thanks.

 

The coolng efficiency lowers as RPMs and speed decrease. You still should not be getting warm air however.... What happens as you slow below 30 but keep RPMs in the 2-3k range?

 

There is a fan on your condensor in your fender that removes hot air while your are idleling. Maybe the fan has stopped fuctioning, or a fuse has blown for that fan circuit.

 

plymouthcolt is correct... check the operation of your AC condenser fan, especially the ballast resistor (great detailed troubleshooting instructions on P-Car)! You should be able to hear the fan and feel the hot air blowing out the vents under the car just in front of the left front tire, with the car at idle and the AC on. The ballast Rs are prone to failure, and prevent the fan from operating on the low speed setting. Resist the urge to use the AC until you have a properly operating fan... you run the risk of overheating the system and creating a refrigerant leak. AMHIK!

 

I have this exact problem when it's pver about 95 degrees outside

 

I discovered that my condesor ballast resistor was gone. The condensor fan will cycle between off and high speed rather than using low speed w/o the resistor. In my case, replacing the resistor stopped the high speed cycling of the fan, but did not make the AC work better at low speed. Maybe there was a few degree difference, but was not perceptible by feeling the vents....
I think its a great idea to see if the fan is functioning at all - you can hear it forward the left front wheel well when its hot outside or idling a while and the AC is on max.

 

Hey tj90... you can force the fan to run on high speed (when the AC is on) by jumpering the relay. This trick, coupled with yearly refrigerant level checks, seems to help keep the AC as cold as possible during stop-and-go driving (crucial in Tucson).

 

Brian and others,

The symptoms you describe COULD BE cases of the evaporator icing up in hot and humid weather. If is a fairly common problem and inherent in the 993's A/C design. Read the following thread, it may be of some help.

Basically, if your car is parked and idling with the A/C on and there is NO water dripping from the evaporator drain, them the evaporator is iced up. If there is a puddle of water underneath the car 15 minutes after shutdown, this will re-confirm the ice up problem.

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

Mike Cap
1997 C2
Arena Red

 

Mad: Good point. If I lived in the desert, I would jumper the relay. Be careful with this however - there are alot of amps on that circuit so make sure you use a heavy gage wire!!! Since I live in a temperate climate, Ill just keep the relay in place.
On that note, when I did the resistor replace, I found some crap in the intake of the condensor. It would be worth it to pull fender and even the front bumper and pressure wash out the condensor. Mine had all kinds of debris, cigarette butts from 115k miles of driving. I have heard of birds being stuffed up there.... That would certainly kill airflow at any speed.

 

Mine does the same execpt with my hot air. My heater doesn't work untill I'm at highway speeds, when I drop down to stop an go I get no heat. Wonder if it is related to your problem?

 

Dan - I wonder if you are having problems with your recirc vent servo. If the fresh air inlet doesn't close off completely then you will have a hard time blocking off that cold air entering the mixing chambers. I had that same problem with a stuck servo. When I'd punch it and the engine would warm up, I'd get a nice gush of warm air.

tj - If you jump 85 to 85c you can jumper over the low amp side of the relay. I have heard some opinions that it would then reverse feed a positive voltage back to the ccu and possibly create false signals elsewhere, but I ran that way for 2 years. Could be an alternative at least.

 

Brian- Thanks that's very possible. I'm due for my 90k soon. When I go in I have them check it out. Cheers.

 

Thanks all - I'll check to see if the condenser fan runs at idle. I believe it is, but will double check - I am not getting hot air at slower speeds, it's just not cold - closer to the air temp outside...

 

Had the exact same issue in my '96 C4S. Found the A/C system only had 0.8 lbs of R-134 in it! After a full recharge it blew cold as ice even when dead stopped in traffic.

 

Finally got around to checking out my A/C issue. (No cold air at idle or slow speeds). The condensor fan is not running at all. I have the car up to operating temp & when I turn on the A/C at normal or Max operation, I can see that the condensor fan is not running.

Where do I go from here? Am I looking at Big $$ to get this repaired. The condensor itself is only about 10 mos old.