The Stovebolt Site Forums The Shop Area The Electrical Bay 1957 3200 sending unit???

Took my rig out of storage, fuel gauage showed almost fullwhen ignition turned on, ran out of gas, filled gauage showed full, drove a week no drop, replaced the sending unit showed empty when off, ignition turned on went from empty to full and never dropped as original sending unit. ??? Not certain what to do next. Help. Thanks to all who help me with this issue.

the fact that it moves to full when the power is turned on shows that the gauge is getting power - disconnect the wire at the sender and see what the gauge does, then short that wire to ground and see if there's a change - also check the wire end to end with an ohmmeter .... if the problem developed during storage then likely either something has gotten corroded or the wire got broken

Bill

red58,
Thanks for getting back so quickly. With the ignition on the gauage reads full all the way. Per your instruction, disconnected the wire and it stayed on full.I shorted out the wire to ground and it dropped to a bit above empty wher it usually goes when I run empty, then drops to full empty when ignition is shut off.

assuming the new sender is good [meaning the old one probably was too], you are not getting a good ground to the tank, the sender is a variable resistance to ground, the screws that hold it in ground it to the tank, and the tank needs a good ground which it might not be if the tank is sitting on the original felt and that's under the straps as well - try adding a wire from under one of the sender screws to the cab back wall, floor, strap hold down bolt, or whatever is handy .... the way to check the sender itself is with it out of the tank and clipped from the base plate to ground, run the float manually and watch the gauge

Bill

Tried a ground wire from a sender screw to the floor and no change.Is my next try to remove the sender ground it, then operate the float manually and watch the gauage?or something else?Will get an ohm meter tomorrow and check the end to end wire.

yes, check the float out of the tank, if the gauge swung over when you grounded the wire, the wire is good [and the gauge], and it should work if the sender works

Bill

Bench test procedure: The rear of the gauge should be marked "IGN" and "Sender". If not, just note which is which when you remove. Then hook up sender with a fused 12V to proper terminal on gauge and a wire from sender center tap to other terminal on gauge. Then there needs to be common ground path between sender mounting flange, gauge mounting flange and the neg of the battery/power supply. Hook it up with mostly test wiring, not exsisting wiring if you can. Be sure you have all good contacts (ground and 12V). I use a fused battery charger for my power supply on the bench. Anyway move the float up and down to see if gauge registers empty and full. Make sure all test connections are good. Ohm reading is about 30 ohm, on down to about zero. If it all works, it's wiring and/or ground paths. Corrosion builds at all the ground points, and they all have to be there to get back to the battery. As Bill has indicated, everything is isolated with rubber or pad material. Your grounds need to be from tank sender flange to frame, frame to body, body to engine, engine to batt neg. All that has rubber/insulator mounting to be overcome with CLEAN, SHINNY, METAL to METAL, toothed washer, contact for everything that draws power. After you decide what's wrong, you can use this sender (variable resistor, As said by Bill) to test other gauges that do not work. I.E temp.

Thanks to all, your input greatly appreciated and back on the road. Ran a new wire from sender to gauage and nothing.Eliminated bad wire. Removed new sender, replaced with original, clean terminals, grounds, etc. and back in service, could have been corrosion, removed new sender as suggested to test and foung the flat connector was twisted, from trying to tighten wire , never snug. poor quality???Rechecked everything.Thanks again.You guys are the best.

Thanks to all, your input greatly appreciated and back on the road. Ran a new wire from sender to gauage and nothing.Eliminated bad wire. Removed new sender, replaced with original, clean terminals, grounds, etc. and back in service, could have been corrosion, removed new sender as suggested to test and foung the flat connector was twisted, from trying to tighten wire , never snug. poor quality???Rechecked everything.Thanks again.You guys are the best.