The Stovebolt Site Forums The Shop Area The Electrical Bay gas gauge issues

Installed a new sending unit, new ground from sending unit to truck frame, new 12 volt gas gauge ( recent 12 volt conversion). Have just under full tank. Ignition on and enging running gas gauge remains in just over 1/2 tank- needle has been there since I installed it. Any ideas? Shouldn't the gauge read empty when ignition off? Thanks, Scott 53 1/2 ton.

You said a new gauge, the "new technology" in gauges do not use a spring driven movement like the old ones. Most new gauges just stay where they are when the power is off.

So the needle in the 1/2 position when off is normal? Brand new gauge from Classic Parts. Any thoughts on why not working?

Jim is correct. Some gauges have just a couple of coils that drive the needle and will not return to zero when power is removed. Others have a little more electronics behind them (some have a lot) which will allow a return to zero when power is removed. The real question is why does the gauge reads 1/2 tank when tank is just under full. Are you sure that the sender resistance is matched to the gauge? What happens if you drain some fuel from the tank?

I have the same issue with a new gauge and sending unit from Classic Parts. My tank is full but it only registers a little over 1/2 tank. I bent the float rod some to adjust but it is still at least 1/4 tank off. Good ground and sending wire. I finally gave up.

BobS46 most likely is onto the answer:
"Are you sure that the sender resistance is matched to the gauge?"

What is the ohm rating of your sender?

What is the ohm rating of your gauge?

They should match.

Both are from Classic Parts. Sender is 30 ohmso, Guage 12volt. Sounds like I should return parts and buy from another vendor. Any suggestions? Thanks, Scott

Are these your part numbers?
http://www.classicparts.com/1949-53...2-Volt/productinfo/24-700D/#.VvvVqRIrKdE
http://www.classicparts.com/1931-66...30-Ohm/productinfo/23-522A/#.VvvWBxIrKdE

Maybe they mistakenly pulled/sent this 90 ohm unit that looks almost the same?
http://www.classicparts.com/1931-72...90-Ohm/productinfo/23-522B/#.VvvWIBIrKdE

Call them and ask if the two different-ohm senders have any different markings?

Tim, those are the parts. I will call Classic. Maybe the parts are bad. Scott

Talked to Classic Parts. They said they gets many guages sent back that test ok. Most likely a grounding issue on the gasgauge itself. So this weekend I will pull guage and make sure the fiber insulator on both poles is in place and that there are good grounds on the four tabs holding the assembly to the dash in place. Also, stated that the needle on these gauges will not drop to E when power is off and may drift or read where ever the gas level is. Thanks for the input. Scott

Scott,

If the grounding was/is bad, the needle would peg to Full.

Did you ask how you could distinguish their 30 ohm sender from their 90 ohm sender?

When you have the sender out of the tank, make all your electrical connections, then move the float full up and full down positions. The will read from full to empty or some part is not functioning. Don't worry about any sparks coming off the sending unit - that is normal. Yes, right there in your tank, it is sparking. I used to work for a gauge company.

I did not ask. The unit I have has 30 ohm on it. I will try taking sender out and moving the float.

That is a good idea.

Attach the gauge hot wire to the gauge contact.
Attach a ground wire to an attachment post.

Move the float up and down and see what the gauge displays as you move through the range-of-motion of the float.

Disconnect the ground wire and the gauge should spike to full.

Be careful - good luck with the test.

Tim, on the gauge, don't I attach the sending wire to sending post? Are you saying attach a ground to the guage?

Sorry.

Attach the sending wire to the "sending post"

Attach a ground wire to a fuel-tank attachment screw-hole on the sender.

What about the power line to the gauge?

Yes, hot power to the gauge (at/to E/empty side/post on the gauge)

and, "hot" sender wire to sender (from F/Full side of the gauge)

and, grounded sender "body" attachment ring/plate

I will make sure the ground is good as shown. Will have time Saturday.

Dads50,looks like you have an extra insulation between the gauge and metal?

...pic...

The metal on the back is the ground.

Need good ground from there to housing. And good ground from ...housing... to dash

Well I took the guage apart again and pushed the faceplate oUT some as it was resting on the needle, and after putting it together the needles move in the right direction. Although not perfect as it doesn't go all the way to full it's good enough. Thanks for all the advice. Now on to putting the electric windshield wiper.

.link.



...you should get a good range...

Dads50, you are right. I should getcomplete range. What would be preventing that? As suggested above, I don't want to pull the guage again, but can pull the sending unit out and move the float as you do in the viedo to check the range of the needle. Will do so Monday morning. By the way, you have some great pictures and vedios!

Thanks

Not sure what could be preventing it

If it does the same thing on the bench then it probably the gauge

Those test I recorded are 6 years old.

really so when i turn my key on it pegs to full all the time all i need is a good ground ?? and it will work ??

Maybe, it is an indicator of a bad ground


...example of bad ground at sender...

Gauge pegs full when ground is removed

There are other ground points at the gauge and housing

Pegging full means a direct short in the wire somewhere. In my case the terminal on the gauge was touching the bracket.

Bad ground at the sender also results in a pegged-to-full reading, as nicely demonstrated in DAS50's video..

Here is a pretty good/clear write-up of gas-gauge wiring & diagnostics & solutions:

http://www.fifthaveinternetgarage.com/tech_tips_gas_gauge.php

Great site Tim. Thanks!

Fantastic site...... look at the tech tips concerning other gauges, etc.... worht while saving for reference.

Thanks for sharing.

Bob C

The owner of that website used to be Stovebolt.com's moderator of The Electrical Bay.

Scott;

Did you ever figure out your problem? I'm having the same symptoms. I tested my gauge just before I installed the cluster (using jumper wires) and it worked great. After I installed the cluster the gauge is stuck at just over 1/2 a tank. I'm thinking it's a ground problem, but not sure what to do next. I already cleaned the mount tabs on the cluster before I put it back in. Anyone have any suggestions?
Joe
1953 GMC P/U

Assuming you followed all of the suggestions? You have a ground from the sending unit at the tank to a good ground on the frame?

All grounds are good at the tank. In fact, I can run jumper wires from the back of the installed gauge to another fuel gauge that I hold in my hand and it works just fine.

And I'm hooking the ground (jumper) wire to the back of the installed instrument cluster case, so I'm fairly certain it's grounded properly.

I'm officially stumped. Anyone have any ideas?

Thanks;
Joe

Whew - I think I figured it out. Looks like the problem was that lump of solder between the two studs wasn't quite making contact with the gauge housing. I built it up a little and then reassembled everything. Works so far...

I have a 12v gauge and the original sending unit....all off the vehicle....can I bench test this directly to the 12 v battery ?

There is no such thing as a 12v sending until right?

Cowboy;

This is a cut and paste from a previous post/message. I picked up these tips from fellow bolters. Bartamos was the most helpful in diagnosing the fuel gauge problems on my 58 Burb. Below describes what you need to set up a bench testing station.

If you already have all the equipment, disregard the list below. I never assume that anyone has a full garage full of tools and the knowledge to use them all.


1. Buy a multi-meter. Harbor freight sells one that is acceptable for about $5 on sale every other week. Look at videos on YouTube on how to use. I usually only use two functions. Voltage to check for volts and continuity to check continuity on wires. Once in a while you will use Ohms to check
resistance on items like sending units (fuel and temp).
2. Go to Radio Shack and buy a set of replacement leads/probes for the multi-meter. That is the one shortcoming of the HF multi-meter. The wires busted off the connectors that go into the multi-meter after about a week. Radio Shack sells a pretty stout pair for about $7-8. It is worth the investment.
3. While at radio shack, pick up a soldering iron. I got a table top wand-style for about $25. It's great for doing small automotive wiring. Look on YouTube for how to videos on soldering if you haven't done any before. It's not that hard.
4. You are still in radio shack. Pick up a set of alligator clipped lead wires. I got a set of 6-8 of different colors for a few bucks. They come with alligator clips on both ends with plastic covers over the clips. They are very handy when trying to diagnose wiring. You can clamp the clip on a wire and attach the other end to one of the probes on the multi-meter. Very handy when trying to test continuity on long wires, or one end is under the hood and the other is under the dash.
5. Take two of the alligator clip extensions and cut them in half. Wire a 4-5 foot piece of wire between the ends on one of the leads. That gives you a 5-6 foot long lead wire you can use as described above. Take the second set of ends and solder an automotive fuse holder into it. That allows you to have a fused hot wire lead that is helpful for testing electrical components.
6. Lastly buy an automotive battery charger. I got one at either Sears for HF. It is adjustable for 6 or 12 volts and different amp levels. I use this to bench test electrical items (turn signal switch, fuel sender and guage etc.) Hook your fused hot wire lead to the positive clamp on the charger and then to the item you are testing. Hook the other lead wire you made to the negative clamp on the charger and then to the negative post on the item you are testing. I have made lots of money with this set up. You get guaranteed voltage from the charger and you have an inline fuse (I use a 5 amp fuse for basic testing) and you get guaranteed ground back through the charger to the house current. Bartamos turned me onto this and it's a great setup.

I'm working from memory (about 2.5 years ago now) of my fuel gauge issues. I believe the proper set up is to hook the fused hot wire from the charger to the hot post on the gauge. Run a lead wire from the sender post on the gauge to the hot wire bolt/nut on the sender. Attach a lead wire from one of the mounting screw holes on the sender to the negative clamp on the battery charger. As you move the float on the sender up and down the gauge should move as well. With the sender on the bench you can also use the multi meter to check the resistance. To make things easier I use the alligator clamps on the lead wires to make the connections. Clamp one end to the appropriate spot on the sending unit and the other end to the correct lead on the multimeter. This way you aren't trying to hold multimeter leads in each hand while you move the float with your elbow.