Diagnosing Fuel Gauge

[ardarvin]

I've got a 53 chev car, the fuel gauge doesn't work. I've installed a new sender unit, and one of the micro wires from a coil on the gauge was broken, so I soldered it back on.

The gauge is getting power (drawing about 200mA), and the needle moves from the far left to the empty mark. It never moves past there.

My question: when removing the wire on the gauge going to the sender unit, should the gauge move all the way to full?

Mine does not, so I'm assuming the problem still lies with the gauge?

[Steve E.]

When you remove the wire to the guage it should register empty. Momentarily ground the terminal that goes to the sender unit guage should move to full.

[ardarvin]

Hmmm, according to the shop book I "think" it's supposed to be the other way around:

"...when tank empty...current passes to the tank unit and directly to ground, very little current through dash operation coil; therefore gauge shows empty

As more fuel placed in tank, float raised...contact finger inserts more coils of resistance...additional resistance forces more current through the dash unit operating coil which moves hand to full side of scale".

In any case, I tried grounding it, I tried disconnecting it, no movement. Must be a bad gauge.

Thanks for the help.

[ardarvin]

Yup, twas the gauge. Took forever to diagnose...really weird failure.

The common point between the limiter coil and the operational coil on the gauge was grounding on the gauge mounting bracket...essentially bypassing the operational coil.

One gasket made out of a business card and she all works fine and dandy now :)