280i-thumb wheel does not turn far enough to activate the AC

[MCWEDGE]

MCWEDGE is a US spec '86 DHC with about 26K miles. The thumb wheel turned correctly last year. All the way to the left to open the heater control valve. Most of the way to the right it would come to a "soft stop" indicating that the heater valve was closed. Then it could rotate just a little farther, and that activated the AC compressor clutch switch.

Now it feels like it is jamming before it gets to the "soft stop", and won't go any farther. I can see in there far enough to watch the heater valve moving back and forth. Does anyone know exactly where the AC switch is located and what on the thumb wheel activates it? I'm ready to recharge the AC refrigerant, but of course I can't do that if the compressor can't be switched on.

Thanks!

Jim McPhee
Placitas, NM

[Polly Grigora]

Sorting out the thumb-wheel problem might sort all