Gas gauge

[redtailboa]

Hello
I just installed an underbed tank on my 68 GMC and my gas gauge reads at 3 o.clock . i have read VetteVet and tbone 1964 post and have done all the tested . I can get the gauge to read properly if i unplug the tan wire from fuse panel and put a jumper wire to back of the gas gauge to the tan wire . I tried doing the same with the ground wire on back of gauge to a good ground and still stuck at 3 o.clock position . I am assuming that i have a bad printed circuit board on gauge cluster . Just wondering if that sounds right before i have to pull the dash apart and inspect it . It looked good when it was installed . this is a full restore and truckn has never been on the road yet , but will be very soon Thanks Tom

[gmc684x4]

Have you tested the sending unit out of the tank with an ohm meter to check its ohm range at the tank

Then follow up with the same test with the gas tank wires in the cab to ensure good reading

How much gas is in the tank ?

The new sending unit may have a film of oil covering its contacts wash them with gas

I know my new spectra tank and sending unit are covered in oil from the manufacturer

[dmjlambert]

If you've bypassed the dash wiring by connecting your fuel tank sending unit tan wire directly to the left pin on the fuel gauge, I guess you may have narrowed down the problem. The problem seems to be the connection between the fuse panel and the connector on back of the instrument cluster, or connector on back of instrument cluster to the fuel gauge.

There's not much that can go wrong along 1 inch of a foil trace in the printed circuit. Just inspect it. If needed you can gently clean the contacts in the rectangle-shaped hole were the connector plugs in, and clean the contacts on the plug. It could be that just unplugging the connector and plugging it back in a couple of times will remove some tarnish and get a solid connection going again. Loosen the nut that connects the printed circuit to the gauge, and re-tighten (not too tight). I used some Brasso and a Q-Tip to clean the contact areas of my printed circuit, and also glued down a couple of the traces that were separating from the plastic sheet. You may also have a problem with corrosion in the fuse panel at the tan wire connection to the "FUEL GA" connector. You could probably use a multimeter to check the entire length of the tan wire in the in-dash wiring bundle, from the connection on the fuse panel all the way to the fuel gauge.

[redtailboa]

Thanks for help , i.m going to check the tan wire today from fuse panel to gauge connector before pulling the gauge cluster out . Thanks Again