Fuel Gauge Stuck at Full

[Chado339]

Fuel Gauge on my 88 Chaparrall 198 cxl is reading at empty. when I turn on the key it pegs even more under empty. What is the easiest way for me to test the gauge and or sending unit to see which is working or not or both. If anyone knows where I could find an electrical diagram for this boat it would be appreiated as I am having issues with my nav lights, and horn.

Thanks
Chad

 

[Silvertip]

Re: Fuel Gauge Stuck at Full

You don't need an electrical diagram for the boat. But here is one for the fuel gauge system. Disconnect the wire at the "S" terminal on the gauge or at the sending unit on the tank. See what happens. No change -- make sure the switched +12 volt wire is on the "I" terminal on the gauge and the ground wire is on the ground terminal of the gauge. Make sure the light wire is on the "L" terminal. Measure the resistance of the sender with the sender wire disconnected. Full tank = 33 ohms, 1/2 tank = 109 ohms, and an empty tank = 240 ohms. Do the math for more or less fuel. If the numbers are drastically different than these you have a bad sender.