2002 Grand Prix A/C Troubles

[mtup]

My daughters a/c didn't work when she turned it on for the first time this year. When I started it, the compressor wasn't kicking in so I put my gauges on and she had about 110 lbs. of pressure on the high and low side. The compressor should have kicked in. I checked the fuse in the glove box and under the hood. The both have 12 volts So I pulled the clutch relay and could not find any voltage there at all. None on either side of the contacts or the coil. There was no voltage on either side of the diode. The controls seem to work just fine. When I turn it to max, the blower blows even harder. The a/c button seems to be working fine with it's light and all. It seems the PCM is not sending a signal to the relay or am I wrong. Can anyone tell me where to go from here?

Mark

[brcidd]

At the relay with car running and a/c requested there should be +12v at 2 pins and a ground from PCM on another and then the feed to the compressor- should be katy-cornered from one of the 12v--to determine the constant 12v-- turn car off- and see which ones dies when a/c fuse 10amp underhood is pulled..then jumper it to the compressor feed- should also correspond to the 30 and 87 imprinted on back of a/c relay..if a/c fuse is good then compressor clutch should pull in...

[mtup]

Thanks brcidd. I had tried those things earlier today but you gave me an idea. I jumped 87 out to the battery and the a/c ran great. nice and smooth and ice cold. I still have no voltage at the coil or on pin 30 of the relay. The a/c fuse under the hood and in the glove box are 30 amps each. Is there a 10A fuse somewhere?

[mtup]

Ok, I found the 10A fuse. Put another in and it popped it. Not having a schematic to work with I decided to turn the a/c off and put in another fuse. I had a 15A only. It held so I turned the a/c on. It ran well for about 25 min. and popped it and the ABS light came back on. Not sure how the ABS plays into this. Must be a short in the wiring after that fuse. Could it possibly be behind the fuse box under the hood?

[Tech II]

With the vehicle running, there are 4 contacts to the relay.....2 should be hot......one lead goes to the clutch, and the other lead is the control leg that is grounded by the PCM......

The fact that you have no voltage on any of the pins is the problem.....if the a/c clutch fuse has power to it and out of it, and both the fuse and the relay are located in the same underhood fuse block, then the problem is in the connectors of the fuse block....turn a/c on with car running, and with the palm of your hand, give that fuse block a couple whacks of your hand....if clutch engages, there is a bad connection in there....

[mtup]

I mistook another fuse for the a/c clutch fuse. The a/c clutch/ABS fuse is blowing. It ran really well for about 25 minutes with a 15A fuse in it but finally blew it. Looks like I'm going to have to find a short in the harness. Any idea's where to start?

[brcidd]

Unplug the connector at the compressor clutch coil and replace the fuse with a 10 amp-- if it does not blow- then you have a bad coil on the compressor--double check by doing a resistance check across the coil- should be 3.45 ohms cold...

If it still blows - then look in the wiring harness - especially at the inline diode-- although I thought the diodes were built into the coil connector by then-- if you can see it-- if the coil base has a "+" and a "-" on it then the diode is in the coil- not inline-- these are polarity sensitive- the ones with diodes in the coils-and they can't be wired backwards as older models could.... green is always positive- black wire is ground.

[mtup]

Ok cidd. I will check all these things when my daughter comes back next weekend. The diode is actually plugged into the fuse box under the hood next to the a/c clutch relay. At least I assume that diode is for the a/c. I'm glad you know the ohm readings for this clutch coil. I would have figured the resistance to be higher and may have suspected the clutch coil with that reading. A schematic would be nice. Thanks again for your help.