Technical Fuel gauge troubleshooting

So I just wired up a new set of gauges and everything seems to be working except my fuel gauge. I'm running an Autometer p/n 1424 fuel gauge and the universal sending unit p/n 3262.

When the ignition, ground, and sending unit (signal or "S") wires are hooked up, the gauge reads past full.
When I disconnect the signal wire, the gauge reads empty.
I've tested the ignition and ground wires and they were fine.
When I run a ground jumper to the Signal terminal of the gauge, it reads past full.
When I test the resistance of the fuel sending wire, it reads 29 ohms.
I probably have about 1/4 tank of gas.

Any ideas? Bad gauge? Bad sending unit? Bad wiring?

 

Check to make sure your fuel tank is grounded to the frame and body.





Bones

 

Once I grounded the tank to the frame and body, nothing changed excepted my resistance dropped to 24 ohms. Any other ideas?

 

The website says you should have 33ohms full and 240 ohms empty, so the gauge reading past full at 29 ohms is correct.

Did you adjust the sender to suit your tank so it has the correct resistance at full / empty?

Next step for me would be to check the signal wire and measure the resistance to ground from the signal connection at the tank. I would also check resistance of sender mounting bolts to ground as well.

Regards

 

What should the resistance be from the signal connection at the tank to ground? Same question for sender mounting bolts to ground?

 

I would expect the sender mounting bolts to be 0 to ground. Then the signal point to ground should be between 33 and 240. The fact the resistance altered when you grounded the tank is making me suspicious you have something else interfering with your circuit.

The sender / tank should be grounded and the sender point on the sender should read between 33 and 240 (with the signal wire disconnected).

When you get that right, reconnect the sender wire and check the resistance is the same at the gauge end of signal wire (disconnected from gauge).

 

Did you put the sender in the tank the right way up? If it's the type with a float on an arm I mean.

Sent from my SM-G390F using Tapatalk

 

Thank you guys for your help. I was getting 2.4 ohms at the end of the signal wire but 88 at the sending unit's terminal...bad wire. I was using the truck's original sending wire, which apparently was past its prime.