Toyota Repair: air conditioner, compressor clutch, freon

Question
hi ted-
My sisters a/c stopped working on her '86 Camry.
Its been retrofitted and has been working fine
for years. I ran 12 volts to the compressor and
it still wont come on. Before changing it,
I was told when the freon all leaks out, there
is a low pressure switch which wont allow the compressor to come on. Heres the question, how can
you fill up the system (with a hose and a can) if the compressor wont turn.

Answer
If you are applying twelve volts directly to the compressor it should engage no matter what the freon pressures are, if it doesn't there is a problem with the compressor clutch. Under normal conditions if the freon has leaked out and you connect a can of freon to the low side port the pressure switch will close and turn the compressor on and take in the freon.