A/C question

[macehammerman]

I have an '86 951. When I am sitting still, the A/C blows cold. When I am driving, it blows warm. Any ideas?

Thanks!

[AFJuvat]

Well that is interesting.

Need some more information:

1. Any strange noises?
2. When you say it is blowing warm air, do you mean air that has not been through the AC or do you mean heated air?

Any other clues you can provide would be helpful.

AFJuvat

[macehammerman]

It doesn't really blow warm air like the heater is on, it just doesn't blow cold. No weird noises or anything, and it is fully charged. If I stop for a few minutes, it begins blowing cold again....strange!

[ch944]

What is the compresser doing when it's blowing warm? Is the clutch engaged while it's blowing warm?

ch944

[Lawrence Coppari]

And what is your volt meter doing when it decides to cease cooling?

[Scott R]

Does the symptom change when you use the fresh air/recirc button?

[Bob's944]

I'm thinkin on the same lines as ScottR... sounds like the warm fresh air in coming in and overwelming your evaporator. The mix of fresh air and cold air is controlled by a flap connected to a servo motor. You then have 3 temp sensors, one in cabin, one ambient, and one a/c... if it's stuck open, then at speed i can see where it cause your symptoms.

[lm6y]

Does the later cars use vacuum to control the servos? If so, check for a vacuum leak.

Sounds like Scott R, and Stray are on the right course since you would have more vacuum at idle, causing the flap to only stay in the recirc mode.

[Bob's944]

Looks like there are lil electric motors that do the job, page 211 of the hayne's manual has the wiring diagram. Going by that diagram, I would be pointing my finger at the 'temp mixed flap motor' or one of the temperature sensors possibly. I would bet that that flap motor is stuck in the open position.

[macehammerman]

When I hit the Fresh air/recirulate button, VERY warm air comes in.....I will check the motor and see if something is sticking-

Many thanks to each of you for your help!

Mace