Humvee fuel guage not working

[teamster249]

Im working on my friend's 1989 M998. His fuel gauge is not working. I replaced the sending unit and then filled the diesel tank up with no results. Any help in troubleshooting this problem would be appreciated.

 

[papakb]

The sending unit in the tank is just a resistor that controls current thru the gauge. On the gauge itself the connector with the ribs on it is the +24v input, the smooth one is the tank sender input. Put a variable resistor (~200 ohms) between it and ground and vary it. The gauge should vary between empty and full. If it doesn't then replace the gauge. If it does then there's a bad connection between the gauge and the sending unit or the sender itself is toast.