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?