Can a fuel gauge be refurbished?

I have a 1966 F100 and the fuel gauge is not working. I was getting tired of the all of the gremlins affecting the electrical system, so I had an AAW wiring harness installed. I did not do it. I had a mechanic do it. For the most part, it has worked great. Initially all of my gauges worked including the fuel gauge. I had about a quarter of a tank of gas when I put the truck in my garage to work on the interior. I would periodically turn it on to check how various interior systems worked. One day I noticed that the fuel gauge was reading empty. I was concerned that the gas had evaporated, so I took it to the gas station and put in 7 gallons. Still empty. I pulled the orange wire off of the sending and grounded it. Still empty. I do get some resistance across my sending unit. I replaced my instrument bezel and took a look at the wiring. Those that have installed the AAW wiring harness know that there is the brown wire that goes to the CVU and there is a pink wire for aftermarket gauges and the warning lights. It is not suppose to go to the gauges. My mechanic wired the pink wire to the black with green wire to the gauges together as well as the brown wire to the CVU. I have now corrected that. My old CVU showed just over 12 volts on the input and just over 12 volts output. So I replaced my CVU and that now shows just over 12 volts in and just under 5 volts out. Still on empty.

I get just under 5 volts to the fuel gauge. And slightly less than that on the sending unit side. I decided to try and ground the sending unit at the gauge. Initially it was empty and then after 2 seconds it jumped up to full. It stayed that way after I turned off the ignition. It showed just under 3 volts when it was stuck at full. It is now back at staying at empty.

So I think that having the gauges wired incorrectly may have damages my fuel gauge. My oil pressure and temperature gauges still work. I have a Holley Sniper EFI, so my ammeter is not hooked up. Is there a way of refurbishing my current fuel gauge? If not, are there recommendations for a replacement? Does the 1966 Bronco fuel gauge work in these trucks? I want something that looks original. Or do you think it could still be my sending unit?

On a side note, I noticed that my CVU gets fairly warm when it is on. Is that normal?

Thanks,
Rick

 

All pre-digital Ford (GM and Chrysler) gauges, except for ammeters and speedometers, are simply volt meters with a conversion to some other unit for display purposes. Yes, they can be rebuilt as I had mine done when I restored my gauge cluster. I don't recall who did mine but use your favorite search engine on "Vintage gauge repair". The original Ford design constant voltage regulator lowered the voltage from 12 to 5 volts by rapidly switching on and off due to thermal expansion of the contacts, so yes, they will get warm to the touch. If you ran 12 volts through the gauge for an extended period, then you probably burned it out and it will need to be replaced. It's probably easier/cheaper to replace than to repair. As long as the gauges are set up properly, they are sufficiently accurate to let you know what's going on with the engine before catastrophe strikes; e.g. it doesn't really matter if the coolant temp is precisely 185 degrees or 190 degrees as long as it stabilizes at or slightly below the middle of the gauge. If it keeps going up, you have a problem. Having said that, my measurements on my truck show that the factory oil pressure gauge is quite accurate despite what many keyboard warriors claim about factory gauges.