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Need help with my gas gauge that does not register. 49 half ton. Guage was rebuilt by a reputable gauge restorer and I also sent the sending unit to him which he tested and says is good. Have one wire to the sending unit. What could be the problem? Any suggestions appreciated. R Wise

Are you running a six or a twelve volt system?

six volts

If the gauge is good and the sender is good:

- bad lead/wire to the hot side of the gauge (doubtful)
- bad lead/wire between the gauge and sender unit
- bad ground-contact of the gauge unit to the gauge-cluster-housing (and/or of the gauge-cluster-housing to ground)
- you could also have a bad ground at the sender unit but this would not give you the problem you describe (this bad ground connection would result in a gauge always moving from "Empty" to "Full" when power is supplied to the gauge, no matter how much fuel you have)

Tim

tclederman: thanks, will check these again. New harness recently installed. The third item you mentioned---grounding of gauge cluster housing. How is this accomplished? rwise

rwise,

I do not know how the gauge unit is grounded to the gauge housing on the '49.

The housing itself is grounded to the body by the nut/bolt/screw that holds it to the dash (the dash should be grounded). You could check this ground with a continuity test between the housing and any other clean/bare metal on the body/chassis.

If the gauge unit does not need to be grounded, let's hope that someone corrects me.

Tim

Here's what it should be for a 51, but it's probably the same for yours.
PS of gas gauge dash unit goes to gas gauge tank unit.
DS of gas gauge dash unit goes to ign. switch.
Gas tank sending unit should have ground.
You can take a wire and connect one end to one of the screw holding down the sending unit and attach the other end to the body. Drill a small hole in the body next the tank where it won't show and tap in a small screw if you have too.
Cecil...........

Grounding, grounding, grounding. If gauge was recently overhauled and the sending unit seems fine then it's the connection between.

Your gauge has two active coils which make it work. With the gas gauge powered up, and the sending unit disconnected, it should register full. Now if you put a ground jumper on the sending unit, it should register empty. The gauge must have a good ground in order to work. In addition, one of the attaching screws of the sending unit should hold a ground wire that normally is terminated on the bottom of the cab.

Thanks for all of the input. I will resume work on this bugger this weekend. Will let you know. Rwise