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Hello All,

I'm trying to troubleshoot my gas gauge and had a few questions. First of all, this is a 12V truck with an original 49 suburban tank with a jim carter 0-30ohm new sender in it and a new 12V gas gauge. The truck (I believe is wired correctly). When the truck is in the off position, the gas gauge goes to almost full (is this correct?) When I put power to the gauge, the gauge reads just below half and doesn't move from there. It doesn't matter if the truck is full of gas or empty. It would seem that the sender is bad? I know it's not stuck because I can hear it move up and down if I rock the truck and I know the needle isn't stuck because I can see it. What would cause this?

Thanks

if it's the same as later 12V setups, when power is off it would read empty - when power is on with no sender attached [open circuit] it would jump to full .... maybe you have the hot wire to the wrong post? maybe your tank isn't well grounded, you might try adding a ground wire from one of the sender mount screws to the cab sheet metal

Bill

I had an issue a while back with an aftermarket sending unit for our 71 Bronco.
Turned out to be the new unit was wired wrong when assembled, the gauge post was wired to ground and the ground post was wired for the gauge.

The reproduction 12v gas gauge on my '54 does not return to Empty when the ign is off. It floats to where ever gravity pulls it. Since it is on the top right corner of the cluster, it floats to Full. None of the 12v reproduction gas gauges that I have seen in catalogs are sitting on Empty. It must be the nature of the gauge. The guts of my 12v gauge look totally different to the guts of the original 6v gauge.

I think that your problem is deeper than the design of the 12v gauge.

Two tech tips by Rsndy Rundle, posted many times ...
> Fifth Ave Tech Tips
> Troubleshooting Your Gas Gauge

Check out this site and see if it helps you.
http://www.chevytrucks.org/tech/gasgauge.htm
Harold

Well, I got a new sender and hooked it up to the gauge, it still just reads full when they key it off and will only go to just below half. I know the new sender is a good unit because I checked it. When I move the new sending unit position, the gauge just sits at half. Very odd.

When you say you hooked it up to the gauge was it installed in the tank?
or just tested outside of the tank?

Well, I sorted one problem out - It was the gauge for sure. Quick question, I want to test the new gauge with a new sender that I have. Where do you ground the gauge itself when Its outside of the cluster? I mean, what part of the original gauge is the ground? Is it the part that touches the cluster housing (brass plate on the base where the two posts stick out?

Here are the grounds

...click...

...pic...
The black arrow for the fuel gauge to instrument housing
The white arrow for the instrument housing to truck/dash

Testing outside the truck

If your using power from the truck then run a ground wire from a good ground on the truck to the ear.

If your using a separate battery run ground wire to negative post.

...demo...

Another interesting observation/question. Am I suppose to get 12V touching the ammeter gauge inside the housing cluster? I accidentally touched it while installing my new gauge and got a spark. Then, I put a meter to it, and I got 12V! On the bezel of the gauge? I know the ammeter is suppose to get 12V all the time, but.....

Can't help you with the ammeter question. I'm not running one.

The only thing I can think to check is that it's insulated.
mine had a pad on the back
...pic...

But wait for someone else to advise

It's insulated and working.

The guy who rebuilt the gauges didn't put any insulation between the face plate and the gauge that's riveted to it. Geez.....

On the home stretch. There was two issues. The gauge was bad for starters - It wouldn't go to "E" when I grounded it out.

Then, I got a new gauge and it was reading half the value it should - for this problem, It was the fact that there wasn't enough clean metal between the cluster housing and the gauge itself. (thanks dads50) I cleaned it up and problem solved. Seesh!

As for the ammeter gauge feeding power throughout the entire gauge, it seems that this is normal.