Fuel gauge won't work!

[GM72K10]

Have everything working on my M1028a1 except the volt meter and the fuel gauge. There is power to the cluster in the dash (when I pull out the gauge) and the gauge worked in my parts truck. there is also power back to the fuel tank sending unit. I have tried two different sending units, cleaned the ground wire from the sending unit at the tank to the frame, and nothing. Took the bed off the truck, again, and took the sending unit out, don't see anything wrong. Truck runs but sure would like to have a working gauge. Am I missing something?
Aanother question, is there a relay somewhere for the volt meter? The wiring diagram in the 34 manual shows one but I don't see one listed in the 20 manual. Thanks for any help.

 

[builder77]

RE: Fuel gauge won

I am also curious about the volt meter. My gauge stopped working at the same time I did a fuel filter change, but I have never been able to trace the wires to figure out what is up.

 

[GM72K10]

RE: Fuel gauge won

I found the volt meter relay, its up under the dash taped to the wiring harness, its a bosch 5 prong unit and mine was all corroded. You have to take the instrument panel out to get to it though.

 

[ida34]

RE: Fuel gauge won

If it was taped up something is wrong. It should be mounted on a metal mount that bolts under the driver's side dash at the bottom along with the starter relay and the alt 2 relay.

 

[GM72K10]

RE: Fuel gauge won

So what is the relay that's taped to the harness that is up under the dash for? Mine was full of sand and corroded. cleaned the contacts and put it back. got the fuel gauge to work by removing the gauge, popping out the prongs from the back of the dash, sanding the points of contact with the back dash cluster, and now the gauge works!

 

[ida34]

RE: Fuel gauge won

I am not sure what relay it is. None of mine are taped to anything. Do you see the mounting plate that the bolts for the diagnostic connector hold in place? This should have two bosch type basic relays and one big relay for the starter. The two other relays are for the volt gauge and the number two alt. Now that I think about it there is a plastic box with a small printed circuit board that is taped to the diagnostic connection relay. It is a tach buffer if I remember right.