Fuel sending unit ??

[rlason]

I'm in the middle of rewiring my boat. No power or gauges hooked up yet just running the wires. Using a volt/ohm meter to confirm which wire was from the fuel tank sending unit, I touched the meters leads to both the aluminum tank and the sending unit terminal. I was surprised to find zero resistance. Do I need a new sending unit or is this normal? Thanks Rick

 

[Silvertip]

Re: Fuel sending unit ??

Sure you picked the right wire and do you mean zero ohms or infinity? On an ohm meter, zero ohms means the needle goes to Zero (full right) or if digital it actually shows zero. Touch the red test lead to the actual sender terminal and the other lead to the metal shell of the sender. Empty tank = 240 ohms, 1/2 tank = 109 ohms and full tank = 33 ohms. You can do the math for any other fuel quantity. If there is anything else in the circuit, that constitutes a parallel resistance so it will affect readings. Resistance readings for the sender must be taken with the wire disconnected at either the gauge end or the sender end.

 

[rlason]

Re: Fuel sending unit ??

Hi Silvertip, Tank is empty. No hookups of any kind, just a bare tank with the sending unit installed. Touching the black lead to the tank or the sending unit plate and the red lead to the brass terminal = the needle goes full right or zero resistance. Rick