Stop now, before you kill anything. Either take it to someone qualified or
spend some time learning about the system.... this WILL involve PURCHASING
manuals and READING them. If it was all that f*cking simple, do you think
I'd have a job?

Don't mind me, I'm just feeling "verbose".

Remove and hit it a few times.... it didn't work with my hot water tank....
didn't work with the TV..... didn't work with the toaster (though the flames
were kinda nifty)... and it didn't work with the leak in that rear tire.....
I feel qualified to say that hitting broken things may only make them
brokener (is that a word?).

On the off chance that giving a failed part a whack will make it work again
(and it does happen), you will find that you will soon have to give it
another whack. After that, the whacks will increase in frequency and the
part will finally fail catastrophically.... usually taking out some very
expensive, very innocent parts in the process. But that's OK.... I fix this
stuff for a living and, if you ignore my advice, someones profit margin will
benefit.

What I said was: "You do not have to evacuate the system.  The instructions
I gave are from
Ford's service manual. My valve was sticking and a light tap would sometimes
allow the circuit to close and thus engage the compressor clutch."

Also notice I said "light tap" . Once I identified the source of problem I
replaced the switch. It's not an expensive part.

mikepier@optonline.net wrote in news:1122261014.970907.175520
@o13g2000cwo.googlegroups.com:

It WOULD be a pretty good spark and the car MIGHT 'almost die' when the
compressor clutch engages... or it might seem that way.

But I assume you jumpered between the switch connectors, not the switch
itself.
Whatever... the fact it had voltage means either the switch is bad or the
system is low on freon, which should rule out any problem in the controls

Install the jumper in the connetcor while the A/C  is off then switch it
on

IF the engine DOES indeed bog down seriously then you may well have a bad
compressor. OR it's overfilled (see below) Or one of a few other problems
requiring someone really familiar with the systems to look at it.

If the engine merely drops a little under load.. check at the firewall,
to see that the line going from the condenser (fonrt of radiator) to the
evaporator (inside heater box) gets cold, if it doesnt within a few
seconds, stop immediately.  You either need freon or there are other
serious problems.
If it does get cold replace the switch.
- - - - - - - - - -

The third wire is likely there as a convenient junction point... not
unusual.
- - - -  -
My question is how a "mechanic" can determine that the system isnt low on
refrigerant if he didnt know for sure that it was an electrical problem
or not.

The system HAS to be running to test for adequate refrigerant.  There is,
otherwise, NO static pressure test that will determine that.

If you have 2 oz or 2 lbs of freon in there the pressure will be the same
unless it is running.

HOWEVER!!!!  If he 'knows' it has enough because he FORCED it into the
system... then you MAY ruin the compressor becuase it is overfilled!

Which WOULD account for the engine laboring mightily when you switch it
on.

Which, in turn, is why I got my certification and do my OWN freakin A/C
service - House and car!  
Half those guys cant even explain what terms like superheat and sub-
cooling mean in practical terms