Fuel gauge problems

[Russell]

One of the things I knew I had to repair on the boat I just purchased was the fuel gauge. When disconnected it reads empty and if the signal wire is touched to the ground wire it reads over full. I have read that this means the gauge is OK. I purchased and installed the WEMA sending unit (240-33 ohms) and the gauge seemed to work at first, became erratic and then pegged at over full again. I checked the resistance of the sending unit and it reads 135 ohms which is what I expect with less than half a tank. I get 12.5 volts from the sending wires on the gauge and back at the tank. I removed and replaced all the wires on the back of the gauge and it still pegs above full. Is it time to buy a new gauge or is there something else to check?

[RobS]

What do you mean by "removed and replaced all the wires on the back of the gauge" ? Could be the signal wire between the sender and the gauge is shorting to ground somewhere, or did you replace that wire (complete homerun from the gauge to the sender) ?

[Russell]

Rob, I just loosened the nuts and made sure the connections were not corroded. When everything is connected and the ignition is on the VOM shows 12.5 volts between the signal post on the gauge and the ground so I doubt the signal is grounded. Also when the wires are disconnected from the sender the gauge reads empty. I ordered a new gauge. At $22 it is cheaper than hiring someone to look at it.

[Russell]

FYI replacing the fuel gauge solved the problem. A funny thing is that the instructions that came with the gauge described how to test a fuel gauge by disconnecting the signal wire and it should read empty and shorting it to the ground and it should read full. The old gauge did exactly that but it was still no good.