VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 1935 gas gage

My gas gage goes from resting below E to jumps to E when I turn on the key. I've taken the sender wire off and ground the post and it does the same thing. I've tried this on 3 different gages and the result is all the same. I've read if I do this the gage should go to F.

how do I test the gas gage to see if they are good? If the float stays at the bottom of the tank, would this happen? I would think taking the sender wire off and grounding the post it read F. but I find it hard to believe all 3 gages are bad.

Pete

When you ground the wire that goes to the sending unit the gauge should read empty. When you remove the wire from the sending unit it should read past full.

Make sure that the gas gauge is grounded to the dash and that the dash reads ground back to the battery. Most times the dash has been painted. bare metal on the cutout hole ring to the gauge side is required.

Yes, Terrill is correct. The gauge housing itself has to be grounded to work correctly.

when I ground the gage housing it goes to full. So this tells me the gage is ok? I have a new wiring harness on it, so I think that could eliminate a grounded sender wire. can you reach the sender unit wire thru the drain hole in the tank so I can manually push it up to see if the gage reading changes? I hate dropping the tank again (3rd time) if the sender unit is ok.

The first step I recommend is to determine why the gauge itself is not grounded and fix that issue. That needs to be corrected before the rest of your troubleshooting will deliver consistent results.

Then I would determine what happens when you disconnect the wire that goes from the gauge to the sending unit at the gauge itself. Use a jumper wire to ground that post on the gauge.

Then reconnect that wire at the gauge and disconnect it at the sending unit. Next ground the sending unit end of the wire.

I would also try to get a resistance reading from the sending unit. A zero reading means empty and 30 ohms means full.

Empty is the same as grounding the wire from the gauge to the sending unit. If you disconnect that wire it should read full.

The sending unit also has to be grounded If you painted the fuel tank or hanger straps or put some type of anti-rattle material in the straps there might not be a good ground to the chassis and back to the battery.

Many times people will paint the straps to the gas tank. This also removes the ground from the gas tank to the body. If you did this then you will need to place a ground wire to the frame from the gas gauge at the tank. I took one of the bolts that holds the gas gauge and hooked a ground wire to it from the frame. These two areas are the most overlooked when restoring an old Chevy.