Electrical Question

KBM · April 23, 2003

I'am doing some troubleshooting and the service manual directs me to the VCM module connector C2, cavity 9. This is on a 1996 Silverado 4 wheel drive half ton. I've looked in the service manual but can't find a picture that identifies the different connectors or the individual cavities (pin) locations on the VCM. Any help that you guys can provide would be much appreciated. I hate going to a dealer.

Import Hater · April 24, 2003

Is this from a GM Service manual? Try looking in the electrical component locator. It's a shot in the dark, but worth a try. And what exactly does VCM stand for. I'm blanking out. Vac. Control Module? ???

Rob

KBM · April 24, 2003

Rob,

VCM stands for vehicle control module. Not sure about everything it does but I'm having trouble getting my A/C compressor to turn on. The relay is good and the manual shows it's input coming from the VCM but I need to know which connector and pin it comes from so I can check the continuity of the wire. I found the VCM location in the manual but the picture I have did not have the connectors numbered. I will do more searching tonight. Thanks for you help.

Import Hater · April 25, 2003

Ahhhh, now I remember. There's been so many different ones over the years. ECM, PCM, TCM, BCM....bah!

Since you're dealing with the A/C system, you may run out of things you can do since you could come on a point where you need a R134A recylcing machine.

So if you're compressor clutch is just not coming on, you'll need to see if the computer is sending the A/C request signal. I assume this is what you're trying to find that connector for. Try looking in the electrical wiring diagrams. They usually show you all the wires/connectors in a schematic format with the connectors and cavity numbers. And more importantly, it will tell you the color of the wire on that cavity you need to probe.

If you're getting the A/C request signal, and the relay and fuse is good, your problem is probabaly the clutch. Pull the connector off the clutch and check for voltage with the A/C set on. If you're not getting the A/C request signal, the VCM is being overridden by most likely the pressure cutoff switch. You can check that by unplugging the connector from most likely at the receiver/dryer and jumping it with a paperclip. If the clutch engages all of a sudden, then you could have a bad swtich, an overcharged system, or some type of blockage in the system...no matter what you'll need to take it to a shop to hook it up to the machine.

Rob