The Stovebolt Site Forums The Shop Area The Electrical Bay Troubleshoot New Fuel gauge

installed a new 12 volt fuel gauge from classic parts. on my 1950 3100

It reads E with 8 gals of gas I put in it today. The tank has more than 10 gals in it now.

I installed a new spectra fuel tank. new 30 ohm sending unit.

ran a wire from the sender to the gauge, and a ground wire from one of the screws on the sender to ground under the seat/bottom of cab.

brought power 12v to the other post and the gague. As soon as I turned key the needle went to E.

So Far I took a ohm reading at the sender. 20 ohm's

Ohm reading at other end of sender wire at gauge, 20 ohm's

Volt reading at gauge post 12v

Disconnected sender wire at new gauge, and applied power to gauge, Needle didnt move off E,

I used this photo off internet as reference

Is there anything Else I can check before I call classic parts about a bad new gauge?

Its a new gauge so Im hoping Im missing something.

Thanks

are you sure it is for 12 volts and not six........but then the original six volts were 30 ohms

wonder how you had a drop of 10 ohms... I do know that the gauge and sender have to match as far as ohms and I am sure you do also,I had trouble once with one being in the wrong box that was suppose to match and did not, dont think that is your problem,

hold on for awhile, someone will chime in and give you a good answer..

Sounds like you did it right unless you accidentally put power to the wrong side of the gauge.. Time to make the call.

I did check that last night.

At least the box it came in says 12 volt,white needle. 1950-53

I cleand the area where the ground wire from the tank is attached under the cab.
That made no change. still sitting on E

Thanks

Hi, dads50, First, run the ground wire to sender it self (to the round plate that holds the float), if that dose not work , try using a jump wire between the sender wire at sender unit on the fuel tank and touch it to ground quickly and see if the needle jumps to full(just on/off as fast as possible)if it swings to full wiring is good, sender bad or stuck in the down or empty position.

troubleshooting continued

Per hippy
ran ground wire to sender post No change

Tried jumper wire between sender post and good ground. touched quickly. needle did not leave E

cleaned undercoat off bottom of cab where ground off sender screw is attached

checked connections on back of new gauge.

removed new sender from tank. Ohm checked it through cycles up and down runs from 2-30. so its good.

Im back to a bad brand new 12 volt gauge from classic parts.

Problem is I purchased it months ago. Hopefully its returnable. Also the 60lb oil gauge I bought at the same time snapped at the threaded connection. I just about had it with this repo overseas stuff.

I will put a voltadrop in line just to make sure they didnt put a 6v gauge in a 12 volt box, as suggested above.

Im down to pocket lint on the budget

Thanks again

With power to the gauge and no ground it should read full. When the sender wire is grounded it should read empty.

Get yourself two six volt batteries.
Get two 15 ohm or three 10 ohm resistors.

Put batteries and gage and sender on bench. Connect batteries in series but leave a connection between them to get six volt.

Then using proper polarity connect gage to one side of battery then otehr side to sender and ground of sender to other side of battery. Would do six volt first. See if works. Now replace sender with resistor if 10 ohm should give 1/3 scale if 15 one half. If works with partial resistance ie 10 or 15 and works with full ie 30 you have a 6 volt setup. IF not then connect to 12 and try again.

Dan Bentler

Get yourself two six volt batteries.
Get two 15 ohm or three 10 ohm resistors.

Put batteries and gage and sender on bench. Connect batteries in series but leave a connection between them to get six volt.

Then using proper polarity connect gage to one side of battery then otehr side to sender and ground of sender to other side of battery. Would do six volt first. See if works. Now replace sender with resistor if 10 ohm should give 1/3 scale if 15 one half. If works with partial resistance ie 10 or 15 and works with full ie 30 you have a 6 volt setup. IF not then connect to 12 and try again.

Dan Bentler

that is funny....Im down to pocket lint on the budget...
never heard that one and Iam old man

usually hard to get suppliers to take back electronic merchandise, especially if it has been put on a vehicle but good luck with trying

Is the guage cluster installed in the dash? The guage housing itself must be grounded in order for it to read correctly. Sometimes when the cluster is installed in a freshly painted dash this problem will occur but can be remedied by installing a ground wire from the cluster to a good ground.

respectfully disagree waldo53, The fuel gauge is insulated from the housing by the cardboard, grounding through the sending unit is what makes it work.

And respect to you as well FGT but I'm stickin' to my guns here. This shows how fuel gauges work. In this case the "down" coil which is our "operating" coil needs a physical ground.

If you do a search for "bench test" you'll see that you can't get one of these goldarned things to work until the guage case is grounded to the same ground as the sender.

Hi, dads50, waldo53 has it right.

OK, I stand corrected. What is the cardboard ribbon for? Is it just to prevent the posts from getting jumped by accident?

Ok
Here is the latest

I removed the cluster from the dash. Thinking the needle was stuck I freed it up by hand. Placed the needle by hand at 1/2.

Placed the power it its post and Touched the sender wire to its post. The needle was driven to E.

I placed the needle back to 1/2 by hand . Placed the power to its post then ran a ground wire to the gauge sender post. The needle was driven to E again.

This was with the cluster just sitting on the bench seat.

Is this telling me anything?

The cluster is stamped 12v on the back.

The power is going to the post behind the E mark, and the sender is going to the post behind the F.


Again Thank you for all the suggestions.

Hi, dads50 , is it possible that you have a positive ground GMC gage or truck

I dont think its a gmc gauge
pic back of gauge

pic of box

My truck is a chevy 1950 3100.

you can fix it quick with a s/w gauge and sender

not familiar with that? Is it a brand?
I’m attempting to keep a stock look.

back to the pocket lint issue,

May have to do it like the pilgrims’ did back in the day.


Thanks

Trying not to sound like a broken record here but in your tests with the guage cluster sitting on the seat - did you run a ground wire to the guage housing?

Good question.

I May not have grounded the cluster itself while I was testing it sitting on the seat of the truck last night.

I think I may have just hooked up the power and touched the sender to its post and that when the needle wad driven to E.

You got me thinking of this whole grounding issue.

Back in May when I bought this new gauge I had problems with the neddle sitting to high it would hit the bezel face

so I had to make a spacer and glue it to the bezel so the neddle would clear


Pic

Maybe that spacer is causing a grounding problem?
Maybe its keeping the gauge housing from grounding to the dash?

I made the spacer out of a gasket material

Dont worry about broken records. All advise is Greatly appriciated

Thanks

It's hard to see in the picture if your gasket would be isolating the guage from the housing. A simple alligator clip test lead from the guage to a good ground should confirm if that is the problem or not.

yes,stewart warner is an after market gauge, I too like the stock look but I got tired of trying to make mine work,the stewart warner worked well and took about 15 min to install..I never ran out of gas again...lol

In your pics,I noticed that your ground wire is attached to an area of undercoating. Has this area been sufficently scraped down to bare metal? (Again back to grounding issues)

PapaJ
One of the first troubleshooting steps was to take a dremel tool and removed the undercoating under the cab where the ground is attached. It made no diffrence. Good catch.

Im still thinking the spacer I made for the needle to clear might be a problem. It keeps the bezel from touching the gauge housing once installed in the dash.

Had to step away from this gauge due to frustration,
Went to a car show today,

Came home and made a 20 dollar seat cover for the truck. I hated to cover up the green diamond tuck my uncle installed in 1975

Installed a new head liner also.

Ill get back on this gauge problem tomorrow. Next step is to run a seprate ground to the gauge housing itself, as suggested earlier.

If that dose not work Ill have to call fail on this new gauge.

Thanks againg for all the tip's and suggestions.

TRY THIS. There is no proof they sold you a 12 VOLT gauge anyway.

Cut the sender line under the dash. Temporarily install a very small light bulb (like another instrument panel bulb). Operate the sender up and down. You may have to try a few different bulbs until you find one that is 100% accurate. This will work. You will actually notice the bulb will glow a little. It won't fully light up. It's the only thing I found to actually work. Solder the wires to the lightbulb in series with the sender wire when you find one that makes the gauge read E when down and F when up. Reinstall the sender in the tank.

One word of CAUTION. When the gauge reads E, you are not low on gas. YOU ARE OUT!! NO JOKE. Ask my sister. She had to help me push the truck into a gas station.