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One of the last projects on my 54 Chevy 3100 is to get the gas gauge working. So far I am not having any luck and I have went through several troubleshooting steps. With everything I am seeing it should work but it doesn't. I have a new sender in the tank that is grounded very well. The tank is between full and 1/2 full and its reading about 18 OHMs which I think sounds reasonable. The gas gauge is a brand new 12 volt gauge from Classic Parts. At the moment I have the gauge cluster out and would like to make the gauge work before I install it because getting the gauge cluster in and out is not the easiest thing ever. I put 12 volts of power to the terminal labeled +. I put a ground to the back plate that contacts the gauge cluster housing. And I put the sender wire to the S terminal. Whether the S terminal is hooked up or not the gauge just reads Full. If I reverse power and ground the gauge reads Empty. It just seems to be unaffected by the sender. When I say it reads full or empty it goes way past full or empty which I think may be another problem altogether. There is almost 180 degrees worth of needle movement and it looks like there should only be about 90 degrees of movement.Can anyone tell me is this normal? Any thoughts or suggestions why the sender is having no affect on the gauge? Thanks

I forgot to mention the wiring is all new modern wiring so there is little chance anything it shorted.

I would suggest to go by elimination of problem possibility.
First, check resistance between gas tank and a well know ground.
Check resistance between gauge - and a well know ground.
Check resistance between gauge - and gas tank
Check continuity of the wire between gauge and sender (disconnected).
Check wire for short to ground (disconnected)
Check if it's the same wire from tank to gauge
Do you read the same at the sender (wire disconnected), at the end of the wire Gage end (connected at the sender, disconnected at the gauge).
Check resistance between a well know positive and + at the gauge.
Maybe remove sender from the tank and with it properly grounded, check if resistance change.
If all check good, than maybe your gauge is faulty or do not match your sending unit. Double check the instructions and don't assume because wires or components are new that they are in good working condition.

J.F.

I just got schooled up on this!

1. Did you bench test it? If not, take sender out of tank a gauge cluster also. Hook battery positive up to gauge, ground gauge to negative on battery, hook up sender wire to gauge and sender. Once hooked up, move sender to see if gauge moves. If not, trouble shoot.

2. Check sender to ensure it goes through correct range of ohms.
3. Check all grounds (gauge to cluster, etc.)

Once you have it working, put gauge cluster in place (in dash) and check again. Finally use your wiring to see if it still works.

Go take a look at what the guys put on my post which should have been called “gauges for dummies” https://www.stovebolt.com/ubbthread...another-gas-gauge-issue.html#Post1265873


Chris

"Full" reading is a disconnection issue or a bad gauge or sender or no power to gauge. Sender sounds good (as far as reading correct ohms for 3/4 full). If you are sure about the wiring and grounds and power, then you have a new bad gauge. Provided you are talking about a truck that has been converted to 12V. Provided you are sure the gauge is actually receiving voltage. You can not assume the gauge and the sender are grounded just by looking at them and thinking you did a good job. It's a looooooog ground path for both. To be sure, you have to run a separated loooooooooog wire to the battery negative post for each. If that still does not work, take the gauge back.
You have done a good thing. Not installing the gauge until you are sure. The super smart thing is to bench test the gauge and sender together before either is installed. Then you will know it's your installation that is the problem.
Be advised that a ohm test on the sender does NOT verify that it is grounded to the battery of the truck. Attaching a wire from a sender flange screw to a nice bare spot on the frame is the correct way to ground the sender. That still does not guarantee a continuous ground path to battery negative post.

This is your ticket to success.

It’s going to be very easy to test if you remove the sender from the tank.

Connect the + to the sender. Ignition on gauge reads full.

Touch the - to the sender flange and the gage should drop to empty. Because the float is down.

While holding the sender and - wire in contact. Move the float arm and watch the gauge. If it doesn’t move. I’d say it’s the sender. I just installed a new sender yesterday.

Don