The Stovebolt Site Forums The Shop Area Interiors new gas gauge goes halfway and stays when tank is full.

This is for my 52 Chevy 1/2 pickup 12 volt. Any ideas, thanks HUGH

take out the sender, put a temporary ground from its mounting flange to the cab, move the float arm manually thru its full swing and see what the gauge does - could be the sender has a problem, or the gauge needle may be sticking, or you need a resistor to adapt the 6V gauge to 12V - if you can make it go to full moving the float arm, you might need to bend the arm, or you might have put the float in wrong so it's hitting the side of the tank

Bill

So many things can affect a gas gauge, that's why there are so many questions over the years. Ground, as Bill is indicating, is no. 1. Gauge and sender need grounded. Grounds for everything on our old trucks are run thru the frame, engine, cables, straps, dash metal, sheet metal, brackets, component housings, screws, bolts, washers, intimate contact and rust. A huge sectioned path.

I had a problem with the float arm hitting the side of the tank, giving me symptoms just like yours.
Carl

Gas gauge worked, and nothing has been touched except the gauge was sent out with the cluster to be refurbed. I just pulled the cluster back out and removed the sending unit wire, It goes to full, I put back sender wire and it goes back to half full. Going to jump a wire from the sending unit to the gauge to rule out any problems with the wire under the truck. This was all good just a month ago. But your right maybe the float assy has finally gone out, or maybe a bad ground. Will check all of this first thing in the morning, thanks for your quick replies, HUGH

The test is: (if you can get to sender); Remove sender wire from float, it should show full. Will show empty when sender wire held to ground. If it passes, hook up sender to float and ground sender flange, should show full if tank IS full. Work float up and down.
Note: Not sure what you did? If cluster is out, were gauges grounded? Did you remove sender wire from Gauge for the "FULL" test? If so, remove sender wire again from gauge, add a test wire to ground for "Empty" test. Of course you need power to gauge during tests. Gauge body must be grounded.

Removed sender wire from float, its showed full,
and empty when wire held to ground. I did remove float assembly and ground it and move it through its full motion and it still only registers a little less than half full. Do you think maybe my float assy is bad or would it have anything to do with 6 or 12 volt. My truck is 12 volt making my power source to the hot side of the gauge at 12 volts, if the guy that refurbed my cluster put a 6 volt sending unit in would this create these symptoms? Thanks HUGH

there is no such thing as a 6V sending unit, sending units are simply variable resistors, identical for any voltage, for our gauges they are 0-30 ohms, check it with an ohmmeter .... the test you did shows the gauge is working but your sending unit appears defective

Bill

Test the sender with a meter

Here's an example
...test...

Will order a new one, thanks much for all the help guys, this site really makes completing this build a reality, even for a wrench fetcher. Thanks again HUGH

I'm not sure your gauge or sender are bad. If you are using the original 6v Gauge and Sending Unit you need to install a Runtz resistor at the gauge to drop the 12v to 6v otherwise the gauge will only read 1/2 full when it's really Full...Ohms Law.

Mike B

Well I installed the new 30 ohm sender, still reading half full, will order a Runtz resistor and hope this fixes this problem. Hope the resister comes with instructions, thanks again for all the help, HUGH

Did the guy rebuild the gauge to 6 volt or 12 volts?

See MikeB's post above

If you put 12 volts to a 6 volt gauge you might damage it.

If you put 12 volts to the sender post you can damage the gauge

6 or 12 volt rebuild? Not really sure, all I can say is that it originally worked and gauge showed full with 12 volt, now it shows half full with the same 12 volts, he must have swapped out my 12 gauge with a 6 volt during the refurb process.

Might want to call and find out what was done?

Was the gauge original? Or a modern replacement

On some of the modern replacement fuel gauges the needle sits high and can pinch the bezel. ...pic...

Can you post a pic?

I did remove the sender wire from float, it showed full, and empty when sender wire held to ground. That took it through the gauge motion showing nothing pinched. It just goes back to half when all things are hooked back up. Can it really be anything else except the lack of the Runtz? I will order one just to see, if that does not work then I am at a loss as to what is wrong.

It is possible, but you stated it worked before on 12 volts, before it got refurbished?

Did you take an ohm reading at the sender?
If your tank is full is should read 30 ohm

Not sure if he sent me back my original gas gauge. Mine would have had to be 12 volt to work without voltage reducer. If this one is 6 volt then a Runtz should be a fix all for this problem? I got the same 1/2 full indication with the old sender and with the new sender. I did not take a sender at the tank reading of 30 ohm, was kinda assuming that since it was new it would work as advertised. May have to call Bowtie bits on Monday to find out what he used. Hopefully he will remember my exact refurb.

did you try this earlier suggestion?

did the guy paint the inside of your housing?

When I got the new sender I did connect the sender wire and ground the flange and manually moved the float assy, it just went halfway on a full tank. As far as if it is painted inside I did not look inside the unit at all. I would like to think Jeff over at Bowtie bits would know to make sure that it was not painted to insure a good ground?

...here is the back of my replacement 12 volt fuel gauge...
marked 12volt


let us know if he switched you to 6 volt with out telling you. He may have assumed your 6 volt?

Closer inspection of the back of the gauge he wrote 12v in marker on the power lead side, so I would assume he means it is in fact 12v. I came across a a/c delco part nr. u1745 for a gauge resistor, will pick it up in the a.m. I will call Jeff in the a.m. as well to see if he can help. I feel like I am running 3 different directions at once. This is just a circuit with a gauge, two wires and a sender. Never though it could be this hard, again much thanks for all who are helping me through this issue.

hang in there

it's common to have problems with these new gauges.
it comes up quite a bit in the electric bay

sometimes it helps to test on a bench first
..example...

most times its a grounding issue
either the sender is not grounded to the truck body properly, ...example...
...example...

or the gauge is not grounded to the dash properly.

...example...

since it worked before the guy fixed it, I would concentrate on the new components.

If your sender is installed in a full tank I would ohm check it just to make sure its reading 30ohm. That way you can eliminate the sender problem

take a break,
keep us updated so that your experience can help others.

Let me recheck "The test", and the 30 ohms at sender, and all grounding points, and last but not least that Runtz, will get back to you all, again thanks for the assist, HUGH

Went cruising today the gas gauge is heading for zero from half a tank, so seems things are working, just from halfway instead of full.

bend/rotate the gauge needle to read full when the tank is full .... problem solved, just need to watch what it reads when you run out of gas

Bill

Not sure if that is the problem because during "The test" the gauge showed full and empty during the full travel/sweep of the gauge needle. Not sure I could bend it a whole half way without damage.

I might have missed it but I would talk to the shop that did the work and tell them what is going on. I'd rerun your ohm checks first though with the readings at the gauge.

Dennis

well then your float arm needs bending or you've installed it so it hits against the side of the tank .... although above you said it still showed 1/2 with the float moved manually, if now you found that the gauge properly tracked manual movement of the float you don't have any electrical problems, if it works OUT of the tank, it'll work IN the tank

the difference between a "6V" and "12V" gauge is 6V is the original electro-mechanical type and 12V is a modern electronic replacement, the difference is very obvious is you remove the case and look

Bill

I do not see any consideration of 0-30 ohm sender (original resistance-range, 1964 and earlier) vs 0-90 ohm sender (1966 and later resistance-range).

Might that be a factor here? (forgive my ignorance for asking - continuity and 6v/12v are my only electrical understandings).

Will call Bowtie bits in the a.m. and yes will re-conduct the readings, float travel up and down match up to the original sender, float inserted so it travels up and down facing the longest part of the tank. It was ordered as a 30 ohm sender for my 52 1/2 ton pickup. Things seem to work except the fact that it only reads half back to empty, here's hoping a Runtz will straighten this all out. Again thanks for all of your responses.

Wow DADS50, your post makes it sound like the Runtz is optional. I called Jeff at Bowtiebits this morning and he assured me that that gauge is 12v since he tested and marked it 12v before it left the shop, I still have to do my rechecks. Was going to do it after work today but the wind chill is 28 degs. It was 81 degs just two days ago. This weather is crazy. Will keep all posted on the results, thanks again HUGH

I would not make that assumption.

But at least you know your gauge is 12 volts

When I bought the truck back about three years ago the gas gauge did not work, after reviewing all the information I could find on the internet I noticed who ever hooked up the gas gauge crossed the sender wire to the hot side and the hot to sender I drove it like this just using my odometer to tell me when to fuel up for approx. 2 years never really trying to check the status of the gauge. I uncrossed the wire and that fuel gauge worked like a charm. I think that mechanical gauge is a lot more forgiving than we give it credit for.

Ok fellows back in the shop, its not 29 degrees anymore. Checked the sender on an ohms meter this what I got:
1. I tested the sender 1.2 to 33 ohms manual hand sweep of the float
2. I hooked every thing back up and
removed the sender wire reads full, sender wire grounded reads empty.
3. Gauge sender post to gauge ignition post 33 ohms.
4. sender post to cluster housing 25 ohm.
5. ignition post to cluster housing 60 ohms.
6. float not coming in contact with the wall of the tank
7. still having same problem gauge reading to low on a full tank.
thanks much for your help.

not clear exactly what #4 and 5 mean, there should be zero ohms from any ground to any other ground, and no ground to the ignition post .... it may be that you don't have a "clean" ground and are adding the 25 or 60 ohms to the sender 'ohmage' - also make sure the gauge and cluster have good grounds to the dash, if things were painted before re-assembly you're adding ohms to the grounds

Bill

Try grounding the sender to the negative post of the battery with a jumper wire.
Are you one hundred percent sure that the new gas gauge needle is not contacting the glass of the cluster? The replacement ones are notorious for that.
Carl

I removed the cluster from the dash and did my tests with a good ground. Also look at number two in my post above I removed the sender wire from the sender and it swept to full and I grounded the sender wire and it swept back to empty without contacting the glass of the cluster. The only thing here that has changed is the gas gauge. I sent it in for refurb of cluster and the gas gauge before sending it in was working. Just went out and jumped ground straight to the neg terminal on the battery and gauge still not reading the right fuel level.