Lazy Air Conditioner


#1

When I slow down or stop at light, my air conditioner does not put out cold air anymore - only when I am driving at higher speeds on the freeway. Why is this?


#2

Your fan is probably not working. When the engine is COLD and the AC OFF, open the hood and start the car. Get out and look at the engine cooling fan. It probably will not be turning. Turn on the AC. The fan should turn on. Most cars with electric fans should have a two-speed fan or two fans. The fan may be on LOW speed (or one of two turning) when the engine is warm enough and the AC is off. The other fan should turn on when the engine gets hot or the AC is turned on.


#3

What kind of car is this?


#4

It could be a low refrigerant charge. The A/C system relies on a pressure drop internally to cool and when you’re on the highway the compressor is turning faster. This means the high side press. goes up and the low side goes down with vice-versa at idle.

Another possibility is a vacuum operated blend door not functioning properly and allowing heated air to mix with the A/C cooled air.

First step is have the gauges put on it and see what’s happening there.


#5

It’s a Saab 900 Turbo


#6

Thank you. I will check the fan. I recall having this problem once a long time ago and didn’t recall the solution. This sounds familiar. I appreciate your time.