Probably is the CCUnit. When mine failed it would adjust temp but the A/C compressor was on 100% of the time, regardless of button pushed. I lived with that for months but then one day it went to full hot and a day later smoke started to come out of the unit. (I guess it decided I couldn't take a hint). I later discovered my circulation pump was frozen and may have shorted the CCU so you may want to check that too. There are a few places you can send your CCU unit to where they will check it. If you need a new one definitely go the rebuilt route because it's much cheaper than new.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold