Fuel gauge/sending unit selector switch

[alvald83]

I have a 1969 f250 CS. I am able to use both stock fuel tanks by using the fuel tank manual switch next to the drivers seat. The problem that i have is that the switch on the dash, that tells the fuel gauge which sending unit to read, is not working.  I do understand that it could be that switch or the aux. tank sending unit itself.
Can anyone tell me how to test the dash switch before i crawl under the truck to deal with the sending unit.   I was in a bad motorcycle accident a year ago and have a difficult time getting up and down, so i want to check rule things out before i get under the truck.  Thanks Al

[pcmdub]

The fuel gauges work on ohms/resistance. So if you have easier access to the switch, then test the resistance of the wires before and after the switch. The switch either works or doesn't, it would not change the resistance/reading of the tank level unless shorted.

[Mach428]

I believe that these switches can be carefully disassembled to clean the contacts. I've done this on many electrical switches from this era. Once cleaned and lubed, it should work like new.