67-72 Chevy Truck fuel gauge diagnostics 101

[bamabronc]

Originally Posted by bamabronc

More info. With the gauge outside of the cluster and hooked up, it works. I’m thinking it must be something with how I have the resistor on or the wiring coming into the cluster. Does anyone know what the readings should be on each wire at the plug?

Also, feed wire at plug is 90 ohm, but once plugged in it goes to 36 ohms.

[bamabronc]

Originally Posted by 67 Burb

OK. I missed your last post as I was posting mine. Now you know that the sender is OK and the gauge works out of the dash unit, make sure the gauge cluster is well grounded.

Where did you test the sender from? At the sender or from under the dash?

I have tested the sender both in the tank and out. Ohms moved as it should while moving the float up and down. The tank is full and reading 90 ohms. At the dash plug and tank both read 90 before plugging up to the cluster

It’s weird. Seems to work until I connect the printed circuit

[67 Burb]

Originally Posted by bamabronc

Also, feed wire at plug is 90 ohm, but once plugged in it goes to 36 ohms.

Yes, once you plug it in, you are introducing more circuitry into the ohm measurement.

Run a wire from the ground stud on the back of the gauge to a good ground.

[67 Burb]

The one I have the black jumper on.

[bamabronc]

Tried grounding stud with a wire and no change while harness plugged in

[67 Burb]

I'm stumped. All seems to be OK, but still it doesn't work.

[bamabronc]

Here is a great YouTube explanation on fuel gauges I thought I would share. It covers the resistors and such. https://youtu.be/bVT2Jh_p02A

[57taskforce]

I just wanted to thank Vettevet and Tbone for this great thread. I had to replace my gauge resistor but thanks to this thread I was able to get my gauge working again. You guys are awesome.

[TBONE1964]

Originally Posted by 57taskforce

I just wanted to thank Vettevet and Tbone for this great thread. I had to replace my gauge resistor but thanks to this thread I was able to get my gauge working again. You guys are awesome.

Glad the information provided has helped you. It's always a pleasure to help .