My gas gauge works... when it’s out of the car

Question:

I am having problems getting the gas gauge to work properly on my 1965 Dodge Dart GT. I have had the sending unit reconditioned and the gauge calibrated at the same time at a local repair shop. When they were bench tested they were working correctly.

After putting the tank back in the car and reassembling the instrument panel I found that the gauge does not work. The needle comes up to about 1/4 and goes no further, even with a full tank. I have checked for a good ground at the sending unit and tank. Again the instruments were removed and when it is out of the dash the gauge then will register properly. Where do I go next in troubleshooting this?

Answer:

Have you confirmed that the float on the sending unit is working correctly? If the float is not floating as it should the gauge will not read correctly. You confirmed that the tank and sending unit have good grounds but did you do the same for the instrument housing?

A poor ground or something that is causing even a slight amount of power to feed back through the instrument housing will prevent your fuel gauge from reading accurately.