fuel guage stuck on full mark

[Roger B.]

On my 62, the fuel guage is stuck on the full mark, any suggestions

[Roger B.]

Re: fuel guage stuck on full mark

any suggestions on fuel guage stuck on past full makr

[Edward B.]

Re: fuel guage stuck on full mark

If the pointer is in the full+ position regrdless of ignition on or off, it would appear that you have a mechanical problem causing the pointer to bind. Short of removing the instrument cluster to access the gauge, you might remove the cover over the gas tank, expose the electric connections at the sending unit, then make and break the sender and ground contacts in the hope that some sharp electrical impulses might free the pointer (it worked for me on another manufacturer's vehicle). Failing this, and after a fast rap or two to the gauge itself to try and free the pointer, it would appear removal and repair remain the only option.

[John H.]

Re: fuel guage stuck on full mark

This will help with the diagnostics so you can narrow it down:

http://www.lbfun.com/warehouse/tech_info/gauges%20&%20instruments/C1FuelGaugeTech.pdf

[Jack H.]

Re: fuel guage stuck on full mark

John's article presents electrical insight and should give you a proper diagnostic IF the gauge hasn't been 'pegged'...

One electro magnet (fixed) pulls the pointer needle in one direction, while an opposing electro magnet attached through the variable resistor in the gas tank pulls the the pointer needle in the opposite directon. The two electro magnets act to 'stablize' the pointer needle making it resistant to mechanical shock as the car is driven.

You can 'peg' a gas guage in a couple of ways: (1) let the variable resistor in the tank fall or rise in resistance too quickly, or (2) let the gauge loose its ground reference at the dash cluster. Either malady can result in the pointer needle moving beyond the limits of its dynamic range and 'hanging'.

If this has happened, and the pointer needle is now mechanically 'pegged', the gauge could be damaged. If the gauge isn't permanently damaged, you can often recover by either (1) WRAPPING/TAPPING on the gauge to free the pointer needle, or (2) MOMENTARILY applying a reverse voltage (via a small battery) to force the pointer needle back into its dynamic operating range.

In either case, having the gauge out of the instrument cluster and laid on the bench is a big help in trouble shooting...