Instrument cluster wiring/short problem

[snowbuzzard]

1990 chev diesel 1/2 ton 4x4 with sweep gauges.

 

The problem is that when the marker lights are turned on, all of the gauges max out as well as all the idiot lights light up. I know I must have a short somewhere, but does anyone have a location I should center on, or should I rip the whole system apart.

 

The problem happens when the vehicle is running or not, key on or off. I'm going into the dash tonite, any help would be appreciated.

[GM-Tech]

My first question would be, when you turn on the lights, does the backlighting in the cluster work even if the gauges go full-scale when they're on?

 

I'd go right to the cluster and disconnect the lead for the lighting. I don't have a wiring diagram, but that circuit has been a gray wire on GM vehicles since the beginning of time. I don't see why it would be any other on your truck. If disconnecting that solves the gauge problem, I'd next check the cluster grounds.

 

Goofy electrical problems like this are also often due to a poor ground somewhere.

[71GMC_3/4T]

I'd agree on the ground.

My cousin had weird problems in his S-15 Jimmy when he had his lights on where all the idiot lights and T/S and HiBeams all would light up. I finally traced it to a ground cluster above the parking brake handle. Once tightened it never came back.

I checked my S-10 pickup, wires in the same place. I wiggled the wires and they seemed tight. 2 days later mine wigged out like his. Tightened the ground screw and never saw it again.

 

Look around under and behind the dash for any black wires connected to the metal frame parts. Even if it feels tight, loosen it, wiggle it, and tighten it back down. If you find the right one, your problems will likely go away for good.

 

Good Luck and let us know how it turns out!

[snowbuzzard]

Hey guys, trhanks for the quick response. I have the puppy apart right now. I noticed when the 4 ways are on, it does the same thing. Also, if I unhook the interior dimmer, the problem with the running lights quit being a problem. I am hunting ground, I had the same problem with an '86 s-10. I'll keep hunting, usually you find the simple solution after you have everything ripped apart, so I'll keep dismantling. I'll let ya know how I make out.

[snowbuzzard]

I cleaned up and tightened the grounds by the battery and under the realy panel on the firewall. It clicked, and it fixed itself back up. Thanks guys!

 

For the help, I'll post this online manual:

 

http://search.epnet.com/Login.aspx?lp=user...tm&authtype=uid

 

username : rrc

password: rebsco

 

 

enjoy, I'll put it up in another thread.