The Stovebolt Site Forums The Parking Lot '60-'66 Trucks gas gauge

My gas gauge hasn't been working since I started to get the truck back on the road again. I found out the hot wire coming from my tank was severed. When I reconnected it and turned the key on the gas gauge came on. Voila! But when I shut off the key, it stayed on. Not so Voila!. I think the gauge is reading correctly. About 3/8 full.

Thanks in advance,
Mark

When the key is off, the gas gauge may stay in the same position. Dont mean its not working correctly.

That's what I was hoping. I haven't driven the truck for so long I couldn't remember if that was how it was before or not. Thanks a lot
Mark

The wire coming from the tank is not a "hot" wire. It is a signal wire. The hot wire to the gauge comes from the ignition switch usually. You probably know that.
On my 1960 GMC, the gauge goes to E when key is off.
If you are actually saying the gauge never moves from 3/8, onor off, I would add some gas and see what happens. Could be a stuck needle or bad gauge, etc.

I didn't know that. I don't remember how mine was in the past. I thought it went to empty but couldn't really remember. I did find there isn't power to it now. I checked. There hasn't been anything done to the wiring since it's been sitting but apparently something has changed. Thank you for your take.
Mark

There is a tab on the sender flange that has a wire to the back cab wall. that is a very necessary ground. Be sure it's there and has good contact to metal. I assume you have a Chevy truck somewhere between 60-66.

Yes I have a 1960 Chevy 1/2 ton C-10. The ground is attached and looks good. I'll start jiggling and tracing the wires from the gauge too.
Thanks,
Mark

Fill it up and see. Might be ok. If there is still an issue, make sure the gauge has a very good ground also. I learned the hard way. Even if you think its grounded, touch the back of the gauge housing with a ground wire directly from the battery with the key on. If it moves then, bingo. But fill it up 1st to know what level of fuel you actually have.

The tank is full. The connectors must have been bad as I had no voltage to the gauge. I replaced both of them. I now have 12 volts going across the terminals with the key on. The gas gauge showed above full. I thought that did the trick. I shut off the key and tried it a second time. The needle disappeared. I detached the connectors and tested continuity of the gauge. It tested open. No sound from the multimeter anyway.

If you are good with electrical I won't question what you just said. If you are not good with electrical, some of what you said scares me. Be careful, you don't want to burn up the gauge. I have a few questions if you need more help.

I'm not that good with it but replacing the connectors is pretty straight forward. What did I say that scared you? Testing the continuity doesn't seem too scary but I'm sure you know about electrical than I do. I just wondered where the "signal" wire from the tank goes. I wanted to make sure it was in good shape. Something still isn't right so I would definitely appreciate any help.

It's just me not being sure I understand your test. I can only understand your specific issue by asking questions, don't take offense. I understand wiring pretty well.

1. I assume we are taking about the gauge and the sender, so what connectors are "The connectors" ? Actual connectors or crimp terminals or other? On what?
2. "I now have 12V going across the terminals with key on". What terminals? on what?
3. What meter are you using for testing voltages? Multimeter or a light?
4. Needle went above full. Then Needle disappeared....disappeared above full or below empty?
5. I know you know this, but to be sure...the 12V power goes to the gauge terminal on the E side if gauge.

Thanks

No offense taken at all. I really appreciate the help. I can see where it wasn't very clear.

1. The connectors I'm talking about are the ones on the back of the gauge. I just replaced the original "plug" that was on there with some spade connectors. The original style plug was pretty crusty and not getting a good ground I assume.

2. The terminals on the gas gauge.

I clipped my multimeter leads to the wires coming to the gas gauge like you would using the terminals on the battery. I was getting a 12 volt reading. I checked them like you would a battery. I attached the wires to the gauge, turned the key on and tested again. I got a 12 volt reading.

3. Multimeter.

4. After I attached the wires to the gas gauge and I turned on the ignition key the gas gauge needle went just above full. I wasn't watching the gas gauge the second time. I thought I had it fixed. I can't see the needle at all now.

Pegged full equals bad ground everytime. But now you changed something for the worse. And maybe created a new issue.

I see you cut off the connector which is keyed to insure connection is made correctly. Did you see my mention of how it's wired in case you mixed it up and blew the gauge.
You don't usually test a gauge for 12V across the terminals. You test the 12V wire to see that it has 12V at it's gauge end while it's disconnected from gauge and key on. You test the other wire, the sender wire, with it disconnected at both ends by doing a continuity test to be sure it is viable all the way from it's tank end to it's gauge end. Once that is done, you can start testing to see weather it's a bad gauge, bad sender or ground.

As far as ground, you said the sender flange tab has a wire to the cab, and is good. The gauge is grounded, I believe, by a lug on the back of gauge that kisses up against the cluster metal housing, housing mounted to dash, and so on, back to the battery thru the body. You can put a alligator clip wire on that housing and run it to the battery to be sure it's grounded.

These are the recommended tests. Two different methods, same tests. Report what you find out.
Method 1: Key on
Take off wire from the sender, the gauge should read FULL....or even way past full. If you lose ground it will go to FULL also.
Then ground that same that same wire to a good ground. The gauge should read EMPTY.

Method 2: Key on
This is from "The Filling Station" web site
Remove the wire from the contact stud on the sending unit and ground it to the chassis. If the gauge now reads Empty, the trouble is either poor grounding of the sender or a bad sending unit.
If the gauge still reads Full, touch a grounded test wire to the sending unit terminal on the back of the dash gauge. This terminal is often marked with a red tag. If the gauge now reads Empty, the wire from the dash to the sending unit is broken or the connection to the dash gauge is corroded.

This is what I cut off and replaced. Did I change how the gauge was hooked up by doing this? The red wire is still connected to the same side of the gauge, so is the brown one. I'll do the testing you described.

Thanks
Mark