Afternoon class,

Got a 72 D100 with the tank in the cab. Gas gauge worked awhile back but now on start up it will move to the E and stop. Won't go pass E. I keep the truck topped off but would like to get the gauge working again. Any recommendations? Thanks guys.

 

Unplug the wire at the sender.... Ground the wire and see if it goes to full? With the key on?

 

It don't move at all

 

Gauge is no good... Or the wire is no good.
Do the same thing at the back of the gauge. If it goes full. the gauge is good. If not the gauge is not good.

 

If this is the only problem you're having with it right now, it might be worth the money to replace the gauge and wires anyway.
For one, your tank is in the cab. So, you won't have to crawl under the vehicle to replace the whole assembly.
And two, when wires or electronic parts start going bad it's usually a good idea to take the time to give the rest of the wires and contacts nearby a look to make sure you don't have more surprises coming up soon. Corrosion and damage often effect more than one wire at a time.
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Which side of the gauge do I ground? There is two threaded rods coming out the back? Thanks

 

Which side of the gauge do I ground there is two threaded rods coming out the back that screw on the board.

 

Should be the same color wire that was at the sending unit back at the tank......