Question on wiring of 97 A/C pressure switch

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.

Reply to
mikepier
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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.

Reply to
Jim Warman

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.

Reply to
Richard

snipped-for-privacy@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

Reply to
Backyard Mechanic

For the record, I know for sure the compressor did not kick on when I jumped the switch. And the piece of wire that I jumped it with ( 16 guage stranded) got hot. It's like as if I shorted out the battery, thats how big the spark is. This car did have some work done on it recently ( again, this is not my car, it belongs to my brother-in-law). So it's possible the wiring got screwed up. But even with the big spark, I would expect a fuse to blow. This is why I'm a bit stumped.

Reply to
mikepier

Which switch are you messing with ?

There's the CYCLING switch on top of the accumulator, and then there's the High pressure switch which is in the high side line, towards the front of the car, by the radiator.

The one you can "jump" to get the compressor going, to install freon, or just test what's going on is the one with ONLY 2 wires back by the firewall, on the accum.

You can also go a different route, and use a test lamp to check for 12v on both sides of the switch. If it is only on one side, then either the switch is broken, or it is WORKING, and the pressure is too low to engage it.

Reply to
Armon Tanzerian

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