VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Gas Gauge Reading

I need help. I know, I know.

Anyway here is my problem: My gas gauge on the grey 41 reads between 1/4 and 1/2 full when the switch is on. Even though the tank is full to the brim.

Now for the question: What is a simple way to check to determine if it's the sender, sender ground, or gauge that is malfunctioning?

I have a spare gauge that may be useful in sorting out the problem.

Thanks,

Charlie

If you have a multi-meter pull the sending unit. Put the meter on ohms, place the red lead on the sending unit wire lug, place the black lead against the housing. Run the float arm from one limit to the other. It should show a smooth transition between ~0 at empty to ~30 at the full position. If that's what you get it's not the sending unit. If you don't get a smooth transition or don't get all the way to ~30 ohms it is the sending unit.

Tiny,

Thanks for the response.

What if it took the ohm meter and attached it to the leads on the gauge instead. Full it should show right at 30 ohms, right?

I hate to have to pull a full tank. It means storing about 16 gallons of gasoline. Over 3 five-gallon cans.

What do you think on just testing the gauge? Think that will work?

Best,

Charlie

It's the sending unit that provides the resistance, not the gauge. Go for a nice long drive. I can access the sending unit from inside the trunk on my '38. I thought you keep saying the '41 is better.......

Uh, let's not go there.

Okay. so its different on the other end of the line? Amazing. I told you I wasn't too sharp.

But no you cant get to the sending unit via the trunk on a 41. There is metal that gets in the way instead of wood. I will drop the tank.

Best,

Charlie

Charlie, thinking about it you might be right and might be able to test the resistance by placing the red lead on the wire at the gauge that goes to the sending unit and grounding the black lead. By ground I mean the body, not the other gauge lug. That won't allow you to test it through it's range of motion but might tell you if it's reading 30 ohms at full. If I'm wrong someone will correct me. If I'm correct and it doesn't read ~30 ohms you'll know for sure it's the sending unit.

Hi Charlie!

There a few simple tests you can perform without removing the tank to access the sending unit.

One is to ground the wire from the gauge to the sending unit. That should make the gauge read empty.

Then disconnect that wire from the gauge that gives infinite (very high) resistance. That should make the gauge read full.

The third test is to simply measure what resistance the sending unit is giving right now. It should be a value probably in the 10 to 20 ohm range based on the reading you are getting.

My best guess is that the cork float on sending unit is saturated and will not float as high as it needs to give the correct resistance.

The Filling Station has a troubleshooting guide that has more details.

Thanks for adding the additional info Rusty.

Charlie
Another quick and easy check is to make a temporary second earth from the tank if you cant access the sender body.
Tony

What if I gook the extra gauge and hooked wires at the inatalled one to it? If it gives the same reading then I will know its in the sender if not the gauge.

Thanks for the responses. Let me just say that my above brain storm test is not owing to any lack of my appreciation for the responses.

Best,

Charlie

That will also work. Remember to ground the external sending unit. You can also use an ohmmeter and check the range of readings on the extra sending unit.

If you pull the wire at the gauge end that goes to the sending unit, and it is not 30 ohms (or more than 30 ohms) from that wire end to ground with the tank full, it is never going to work right until you fix it, regardless of the condition of the gauge itself.

Short the meter leads together and zero your meter first. If theres no "delta" button to zero it with, then note what the reading was when you shorted the leads and add it to the 30 ohms.

If its 0.78 ohms for instance then you need to see 30.78 or more ohms when you check the sender to get to full on the gauge.

I have ordered a new sender.

I thought I might as well do the easiest to hardest in reverse order.

I'll let you know how things progress.

Best,

Charlie

Charlie: Have you ordered a new tank yet ?? If not, another thing to ask is "does the new tank have a drain plug",, As I said earlier, I got one tank from Tanks Inc and another from ??. One has a drain plg and one doesn't. I really don't know now which tank came from who but having a drain plug is nice. If I had to choose between one with plug and one with baffels I would pick the baffels. Hopefully the same supplier's tank has both. Just my opinion.

Dick

Had same problem gauge was not getting a good ground where it attached to cluster also replaced sender works well now.