300E AC problem
 

We've had our 1986 300E in and out of the shop repeatedly trying to fix a stubborn A/C problem. It works normally most of the time but periodically will shut down (blowing only hot air) and then after some time will start working again.

The fan clutch has been replaced. But the problem persists.

We thought it might have been the control panel but that was switched out and the same thing happens..

One theory is that the alternator is not working properly, but there are no other signs of electrical problems. So I haven't replaced this yet. It's a relatively big ticket item and I'm getting frustrated with the mounting bills.

Today something new happened. The control panel buttons actually froze over. Literally, they frosted up.

Any ideas?

looks like the flap for the center vent is not opening when in a/c mode.could be a bad vacuum pod.probably not easy to change on this car.dash may need to come out.there are many posts on this topic :)

I'd take the glove box out and peek inside the dash to see that the vent supply is hooked up. Mine came loose and the air was just going into the dash and not out the vent. If the pods are bad the air should be directed to the defrost vent, but still coming out.

You might also be able to see this problem by shining a flash light into the vent to see that the hose is not displaced.

Glove box removal is 5 to 10 minutes.

Definitely got something loose if the dash gets cold.

You also probably have a bad evaporator temp sensor -- this shuts off the compressor when the evaporator gets close to freezing,and if bad (open) will cause the cooling to stop until it makes contact again. Its' in the side of the case, accesable after removing the under-dash panel on the driver's side.

Also, if the AC quits and won't come back on until you shut the car off and restart, replace the belt -- if it's slipping, the KLIMA relay will shut the AC off until you restart, this is to protect you from a locked AC compressor ruining the belt and causing severe overheating from no water pump.

Peter