wrote in news:1122261014.970907.175520
@o13g2000cwo.googlegroups.com:

> A few weeks ago I posted a problem with a family members 97 V6 A/C not
> working. A poster suggested removing the A/C pressure switch and
> hitting it a few times because sometimes it can get stuck. Well I tried
> that and it did not work, but I noticed that on the switch there are 2
> electrical pins, but the wiring harness connection has 3 wires on it.
> When I tried to jump the switch, I got a big spark and the car almost
> died. I thought I jumped the correct pins. Does anyone know how to jump
> out the switch? And what is the 3rd wire for when apparantly it's not
> connected to anything.
>
>

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