Fuel gauge repair HELP

[squarelyfe]

On a 74/75 cluster.. My gauge reads past FULL. I watched a video kinda confirming that if it moves it's getting power at the gauge but reads over because it's missing power/the signal from the sending unit. So... Does my org wire have a crusty contact, loose or broken? My ground at the rail was removed and cleaned at the ground contact and frame scratched clean where it meets. I've been dreading the idea of dropping the tank but don't see my fingers getting in there from below. Wiring issues aside, how many have had it be the sending unit VS missing or dirty wire in this situation of overfull reading?
It would be nice to be able to reach it and maybe pinch the thing so it's tighter clean up the inside of the contact point and the stud. The other day I have the cover off so with my finger I moved the needle to the E side and landed around qtr tank, turn the key on and instantly goes over Full. Was the quarter tank a false reading or does that mean it'll probably work once I get power on the other end of the things? Probing for power at the sender is probably my first move if I can reach it otherwise I gotta drop the tank. Think I remember others touching ground to the power wire or vice versa making the gauge do the opposite direction.



(middle finger in the air)

 

[Dmack]

Past full means you have an open circuit. Usually means a bad connection, broken wire, or bad sending unit. Needle past empty is grounded.

 

[squarelyfe]

That's what I'm saying, it's got to be the power wire is corroded loose or broken OR sender that is bad. I get that with the tank down and the sender out I can test the sender to see the ohms and the resistance I was just hoping to avoid all that and get the quick answer from a few people have gone to the exact same thing to know for sure before I curse a lot. I may not be able to avoid dropping the tank because of location...uggg

So if I touch the ground wire from the sending unit to the positive on sending unit and the needle goes to E side does that confirm it's the sender that's the problem?

 

[Dmack]

Sounds like it. That shows the gauge is working, and tells me the wiring is good. I have had several bad sending units with open circuits over the years.

 

[75gmck25]

Do you have single or dual tanks? With dual tanks the sending unit wire takes a very long path up and through the dash switch, so more places for it to be broken or have a connection corroded.

 

[squarelyfe]

Single tank, 2 port sender. With the key on I just got power at the sender wire.