I have a 1967 Cutlass Supreme Holiday Coupe. I'm having an issue with the fuel gauge. I have a new fuel sending unit, and it did send appropriate signals when I installed it 2 years ago and all worked fine for about a year and a half. I no longer get a reading on the fuel gauge, it just sits at about 1/2 full. As a first step, I was going to test the gauge today based on information I found on this website..... https://www.grainews.ca/machinery-sh...ty-fuel-gauge/

I pulled the gauge out of the dash and now I really cant see how it gets any signal at all.....

Question 1: Is our gauge a thermostatic or a balancing coil type of gauge?
Question 2: How does it get a signal since there are no wires actually going to the gauge?
Question 3: Is there really supposed to be a wire feeding the signal to the gauge or is this part of the circuit board and I have a connection issue there?

Thanks!

 

Here are some pictures.....






How can I test this gauge?

 

The top two studs appear to connect to the coil of wires wound around the whitish material. I suspect current flow through that is what causes the gauge needle to move.

The sending unit is merely a potentiometer (variable resistor) that changes resistance as the float moves. Most are 0-90 Ohms, with 0 = empty and 90 = full.
The varying resistance changes the amount of current flowing through those gauge windings, which in turn causes the needle to move in relation to the float position.

 

Thanks for the tip fun71. I was able to test the gauge using your info and the info found here (https://www.grainews.ca/machinery-sh...ty-fuel-gauge/), my gauge tests out fine. However, once back in place in the dash, things were not working again. I discovered that one of the primary posts was not tightening up as it should. If I press there, all worked and I got a good reading. So, I have added some steel wool to the bad screw and added dielectric grease to both posts, hopefully, this will get the gauge reading properly again!

 

There's a lot more than just the gauge there. There's the circuit and the sending unit, all of which have to work together. If the gauge works, great, but then you need to figure out what isn't working and it could be back at the fuel tank.

 

I was able to test the gauge, then I tested the wiring from sending unit to gauge. That all tested good. Then I put it all back together and that is when I noticed the post on the gauge that wouldn’t tighten. I’ve now got that tightened and dielectric grease applied to the connection. I am getting a valid signal from the sending unit to the gauge but I don’t know what is really in the tank yet. The gauge shows a half tank which is about right for the miles I’ve driven since the last fill up. I’ll refill in a couple of days and then I should really know of it is all correct now.