Gauges acting up when shifting to reverse 1990 c3500
 

When u shift into reverse my gauges go crazy, pegging out, etc. Bsck to normal in drive. Any ideas.?

Re: Gauges acting up when shifting to reverse 1990 c3500
 

I'm no expert, but most of the instrument cluster problems seem to devolve to a grounding issue. If your cluster is not grounded well ANY input to the cluster tries to go to ground through the gauges.

My truck worked great during the day, but if I turned the headlights on or hit the turn signal the gauges went plum crazy.

Sometimes just pulling a new ground to the cluster solves it.

Re: Gauges acting up when shifting to reverse 1990 c3500
 

I agree it sounds like something is losing ground.

Check all grounds.

The instrument panel grounds at a screw next to the ALDL connector.

There is a ground wire between the back of the passenger side cylinder head and the fire wall.

The ECM and engine sensors ground at the front of the intake manifold under the front intake bolts/studs or by the thermostat.

Check the ground between the negative battery cable and the fender.

Test for voltage between the engine block and the negative battery bolt.

Re: Gauges acting up when shifting to reverse 1990 c3500
 

Tinkered with it this weekend. The battery is grounded the engines grounded to the firewall so now I guess it's time to open the dash up. When you turn on the headlights all the gauges stop working. Still love the truck, just gotta find these gremlins. Lol

Re: Gauges acting up when shifting to reverse 1990 c3500
 

Short in that circuit or bad component. I'd replace the switch and check wiring if that didn't do it.

I had a problem like that in the fuel heater circuit in my '92 diesel. It also had a stalling issue when pulling off after idling when warm, which is why I suspected the fuel heater. When fuse blew I lost gauges. Dealer couldn't figure it out and kept giving it back. They never put the two together when all the time I kept telling them check that circuit. I figure it was not cutting itself off once warm and evaporating the fuel in it. They'd say they couldn't get the 25a fuse to blow. I told them put a lighter fuse in. Guy says you can't put wrong fuse in and I told him no harm from a fuse that blows before the proper one does. He said I guess we're just a bunch of idiots. This was after several trips (warranty), so my reply was to thank him for saving me the words. I'm a shade tree mechanic and I could figure that out. I suspect the switch is shorting.