All GM and several other manufacturers use this wiring
for their fuel gauge. I believe some Chrysler products tie the ground
at the tank and gauge with a second wire.
The Tank has a variable resistor and gauge moves the needle in relation to resistance as long as the voltage is constant.
apply any current to the wire from tank to gauge. You will burn out
the hard to find sending unit and might even explode the tank.
If your system is connected as above but the needle doesn't move when you
fill your tank, Test as follows: Disconnect the wire to tank.
The gauge should read full. Ground this wire, and the gauge should
read empty. If it doesn't move, be sure you have voltage to the gauge.
Check to see that the needle isn't bent. If not, the gauge is shot
and must be repaired.
If the gauge moves with the above test, pull the sender out of your tank. Check to see if the gauge moves when you move to float up and down, remembering to ground the sender. If not, the sender needs replacement. (The Stewart-Warner senders have a difference resistance and won't read correctly when used.) You are lucky that all GM vehicles use the same resistance in the sending unit for 6 & 12 volt systems. If the needle moves when tested, but always reads empty, see if the cork float is saturated or the brass float is full of fuel. If it works sporadically, Ground the tank at sender. The tar paper on the straps are not a conductor.
I would like to thank the Royal
Mail for printing this page in the September 2000 issue on page #19.
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