Packard Forum Index » V-8 (1955-56)

Hi everyone. I have a question regarding my fuel gauge on my 56 Clipper. It was working fine and has a new sending unit, but now its jammed on 1/4 of a tank, even when the ignition is off. I'm guessing I need a new gauge. I've checked the voltage coming out of the 5v regulator and it seems to rise to 5v then back down to zero and so on and so on. Is this normal?

The operation of the regulator sounds normal. Regulator is in fact a bimetal element that bends to open and close a contact. There is a heater that gets power, heats, bends the strip to open the contact and when that happens the heater cools and contact closes again. This cycle continues as long as it is powered. The timing and duration of the on and off 12v pulses as influenced by the total load of the gauges gives the averaged 5v output specified. Because the gauge bimetal is relatively slow to respond the short 12v pulses are not on long enough to make the gauges react so are not passed on to the needle.

It could be the gauge itself has failed or something has shifted so the needle is touching the glass.

The gauges are operated by a heater element wrapped around a bimetal strip. It is possible a shorted wire from the sender could have kept the heater on until it burned out but I would think that would have been noticed as the needle would have been pegged at the high end for several minutes. Usually the gauge will still drop to the low side when off unless the bimetal strip got so hot it deformed.

Another possibility is the needle or entire gauge has been jarred out of position. There is not much space between the needle and glass. There could have been some kind of mechanical shock to the gauge that shifted the mechanism or knocked the needle off its pivot. You might loosen the screws holding the gauge mounting plate to the cluster by a few turns and then put something between the gauge mounting plate and cluster to keep it away and see if the needle starts to respond. If it does then it would be a matter of removing the gauge and seeing what happened.

With it remaining stuck even when powered off doubt there is any issue with the sender or wire but just to rule them out remove the orange wire from the gauge then turn on the ign switch and see if the needle changes.

Here is what the output waveform of the regulator looks like.

Attach file:

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  Instrument Regulator output waveform.jpg (44.64 KB)


  Gauge internal.jpg (57.03 KB)

Will do as you say. Thanks again Howard!

I pulled the gauge out and gave the needle a few flicks up and down. Has done the job and working now. It seemed the spring mechanism was stuck somehow. Thanks again Howard for your advice.