Gas Guage Problem

[Jerry Byers]

My gas gauge goes to full when I fill up, but when it shows empty, it only takes about 10 gallons to fill up. This tells me the gas guage is showing about half what is really in the tank.

Any suggestions on how to fix this short of replacing the sending unit?

 

[Ken in MN]

Jerry,
Check and see if the oil and temp gauges are working properly. I'm guessing that there are reading low, too. If so, the silly constant voltage regulator is weak and not sending an average of 5-6 volts to the dash circuit. It is very difficult to troubleshoot this component because your volt meter will fluctuate like crazy since it's an AVERAGE of 5 volts - not constant. The regulator has a really crude method of putting out an average voltage.

If you decide to swap it out, let me know. I have the name of a guy who fabricates them out of solid state components and they put out a constant 5 volts instead of an average.

 

[Jerry Byers]

Thanks Ken......... the oil guage has always read low, but the temp guage seems about right........... my voltmeter does fly back and forth a lot, so maybe the constant voltage thingy is to blame.

For now I am living with it, but one of these days I will take you up and get one of the solid state regulators...........

 

[Ken in MN]

Jerry,
The voltmeter is not controlled by the regulator. Be sure to check the voltage regulator. They get old and corrode inside.
I had the same problem and I think that's the way I solved it but I can't remember the details.
Ken in MN

 

[Jerry Byers]

Thanks Ken. I thought it was probably the VR. I heard you can get solid state VR's too...........

 

[bondobird]

I'd like one of those solid state units also, please post the guys name if possible.

 

[tb65m66]

Just remember that there are two different items discussed here. The Constant Voltage Regulator for the gauges and the Voltage Regulator for the charging system. The latter is the one responsible for the ammeter's wild swinging. A solid state voltage regulator can be found at O'Reiley's or AutoZone for a very reasonable price. I've got one in the 66 Mustang and will do the same for the T-Bird when the original fails. Many folks like to take the cover from an original and place it on the new electronic unit to ensure the proper look under the hood.

Now I've beaten that horse, I also remember someone mentioning a solid state CVR. That may have been on another forum so your best bet would be Google.

Branch
65 Conv

 

[Ken in MN]

The nice thing about his solid state CVR is that it is adjustable. I had to set mine higher than 5v because, as we all know, the old wiring doesn't work quite as good as when the cars were new. His contact info is:

[email protected]

Working under the dash is never any fun but the unit plugs right onto the existing connectors with an extra external ground. Good luck with the upgrade.

 

[tbird5866]

voltage regulator

Perhaps there would be less confusion if you refer to the "instrument voltage regulator" as just that.