Originally Posted by cashflow55
Guys, need help. I have a standard Stewart Warner fuel guage and that seems to be working properly after a resistance test. I have removed my sending unit from the tank and made sure the ground was connected from the frame to the sending unit and the sending unit wire was connected to the fuel gauge. Fuel gauge is grounded and powered. Checked sending wire from rear to front with meter and it is good. When I move the sending unit float up and down, nothing happens on the gauge. The gauge goes directly to past full when wired and key to switched to on. Any thoughts?? Thanks
Don't feel bad, Girls need help too.
"I have a standard Stewart-Warner guage (sic) that seems
to be working properly after a resistance test". You are speaking in a weak voice here as if unsure if the gauge is okay or not. Unsure if the gauge is okay or not, are we? As you know, there are just a few components that make up this system.
Disconnect all the wiring to the sender and check it out using an Ohms test. Only two terminals on the sender unit, so set your meter to Ohms and moving the float up and down, you should note a change in the signal from 0 ohms to around 90 ohms if it is a GM product. That means the sender is going it's job. Reinstall the sender and leave the sender wire & ground wire disconnected for next test.
Turn on the ignition key to the "On position", set your meter to DC voltage and with one probe on the sender wire & the other to the ground wire on the frame, measure the voltage. You have 12v or better, then good.
If you are showing less voltage, bypass the ground wire and look for another place to check for a better ground. Even if you have to run a dedicated ground from the battery for testing purposes, find a ground that will allow you to eliminate the present ground wire as the culprit. Just because it is bolted to the frame does not mean it is a good enough
This is why we are using a meter instead of our eyes to test this.
If you have now rediscovered a good solid 12v after bypassing the present wire grounded to the frame, repair the bad ground cable connection and verify that the ground is good by repeating the 12v test between your new ground and the sender wire. (sometimes the frame may need additional grounding from the battery to get this voltage).
After these tests, we have verified;
1. sending unit is operational and ohms out 0 to 90 ohms during operation.
2. 12v between ground and sender wires at sender connections. (means wiring path to sending unit is good, both 12v and ground).
At this point, and because your gauge goes to full when the key is switched to the on position, I would check the ground wire to the gauge for proper ground. I would take a test lead and wire to the ground side of the battery and see if that did the trick.
If nothing, then I would scrap the gauge. If you had a variable resister with the value of 0 to 150 ohms, you could wire it to the gauge and check the operation of the gauge that way if you wanted to nail it down completely, but at this point, I would toss the gauge if your current sender checked out okay.