Hot only 300E HVAC

[Beagletech]

Help, I need to fix a 1990 300E with cliamate control that is hot only. Any ideas? Presently it is either hot or off. Can't blend the temperature. Thanks, Dale

[jim16671836]

Do you get any air at all when you have the AC on?? If you get air then you need to check your compressor with the engine off to see if it turns. If it is locked up then you have a bad clutch...If it turns freely then you need to see if you have a pressureized system. If no pressure you have a leak. If you do not get air when the AC is on then you have you have problems that are electrical and I can't help you...Maybe this will get the answers and suggestions going your way...Jim

[Beagletech]

Thanks Jim, this is a cool site. After I posted, there were some links shown for similar threads. Nice feature. I did some reading, and am now more familiar with the mono valve and the aux water pump. It's my boss's car, and I am presently going on what he told me it's doing/not doing. I'll do some checking and post again. Dale

[Beagletech]

I cleaned the temperature sensor, and checked out the HVAC myself. The system seems to respond properly to hot and cold settings of the temperataure wheel. A cool setting, activates the A/C compressor and blows cool. A hot setting blows hot. The actual issue is that once the temperature is set at say, 72 degrees F, the temperature seems to get hotter and hotter as the car is driven. Does this sound to you like the monovalve is hanging up? Thanks, Dale