I had the same problem with my '85 Westy.  The switch was bad internally.
Replacing it restored full function.

Mike

I just found out today the ac control switch for the amount of cooling (not
the fan knob) seems to be causing the compressor to kick off when you turn
it all the way to max.
If you run it anyplace lower than absolute max the compressor runs.

Is my switch worn in the place it most likely always is used? on max?  or is
there something else going on.

If I run it at 95% is cools fine, just immediately kicks off the compressor
and the radiator fan if you go all the way over.

Help!

Thanks,

Doug