The Stovebolt Site Forums The Shop Area The Electrical Bay gas gage revisited

my gas gage has never worked on my 63 stepside since i have had it. i tried, to no avail , with different part swaps to get it to go. i came up empty handed and just carried a gas can. i may sell this truck but i really want to get it going.

today i was using my limited knowledge trying to figure it out. i think i have the wiring diagram figured out. i get 12v on pink wire from the switch to fuse box. 12v on pink wire to dash connector. 12v going to one side of gage with pink wire. on the brown wire comming out i got less than 12 volts so i thought this is ok well when i got out from under dash i noticed the needle had moved to full from not being visable. i got back under dash and when i plug in the probe to the brown wire connetor, with it plugged in, i could see with a mirror the needle shoot down to 1/2 tank full! when i remove probe it goes back to full.

does this tell me what the problem is? and better yet what can i do about it??? the tank/sending unit was a new unit a couple of years back. the sending unit is grounded, i checked today. the dash and gage is a used one and this is in a 63 chevy with 12 volts and i am not sure if the dash is a 60 to 62 with 6 volts or a 63 with 12 volts.

thanks for any advice for me, the electrical challanged. i had read some stuff years ago about this, but forgot a lot and didn't understand the other half!!

Hy hoggyrubber, the fuel gauge operates by varrying the strengths between two magnetic fields, the stronger the field on the full side of the gauge, the higher the reading (the least resistance from the sending unit). All electrical systems since 1956 have been twelve volts, so that should not be a consideration. Your connection of the brown wire to the gauge, and the resulting change in the gauge reading would say that you are getting at least a partial ground through the brown wire, and the sending unit. So your sending unit would seem to be functioning, at least partially. What I would do now is remove the brown wire from the sending unit connection and isolate it from any metal, then turn on your ignition and check your gauge, if the reading on the gauge is the same as it was with the brown wire connected to the sending unit, then I would say your brown wire is at least partially grounded somewhere between the gauge and the sending unit connection. If the reading on the gauge goes to full with the wire disconnected then the brown wire is okay, and the "problem" is in the sending unit, hope that helps.

thank you for the info 3b! i reread your instructions just now and i guess i need to drop the tank down to take brown wire loose going to sending unit. i installed the aftermarket under the bed tank.
i did check the voltage comming out of the gage and it was around 5 volts with brown wire unplugged, around 1/2 that 2.5 volts with it plugged in. then i checked the voltage wher ethe brown wire goes from fuse box back to sending unit and it was the same 2.5 volts.
the odd thing is when i check it with a probe the needle would jump down to 1/2 tank or jump all over the place back and fowarth. then with the voltmeter it would go down a little it but not all the way to 1/2 tank. the wire going back to the sending unit is a couple of years old i replaced it when i put on tank. i replaced the tank on my 64 and had no trouble with the gage.
do you think i should go ahead and drop the tank and check there? thanks for any info.

Hy hoggyrubber, with the ignition on, anything that you touch to the fuel gauge terminal where the brown wire should go that can reach ground, such as a test light or an electrical meter will effect the reading on the gauge, because it is becoming part of the circuit, hope that helps.

thank you for all the suggestions 3b. i have been working on this off and on for days now and have got NOWHERE! i have about 7 things that are too much for me to figure out and i rotate between them. today, i am am almost ready to reach for the BFH!
i ended up removing part of the bed to test the sending unit. this involved drilling out rivits and taking out a ton of bolts. well when i did it looks like the sending unit is working it has about 2 volts when plugged in and when i unplugged it it shot up to 5 volts at the wire. so then i decided to switch out the dash to another one i had. plugged the new dash's gage in and after i grounded the dash the gage seemed to work! then i installed it and switched over the wiring and NOTHING!
now the pink wire has 12 volts and everything else is dead. the brown wire side, the plug in on the fuse box, the sending unit- all dead. i don't know if i fried something messing around with it all so much or what. i have read the sending unit and gage are match voltage sets, but i don't remember for sure what the tank/sending unit was for, i think 64 to 66- it has been several years back. so i don't know where this leaves me. maybe take a electronics class and buy all new stuff. heck this wiring is a little wicky in this thing maybe i should buy a new harness- all for a truck i rarly drive and can't sell sounds like another great idea- ha ha.

well i kept at this today and i may have made some progress. i put another parts gage/dash incert in and everything is working somewhat. it reads 2.5 volts and the gage registers a little over 3/4 tank. i don'tknow what the problem was. part may have been the dash wasn't grounded since i painted the main dash and the dash insert may not have been grounded. i think i am oing to drive it, still with my gas can, and see if the gage is accurate. it is repeatable for the first time. key off- goes to empty, key on- goes a little over 3/4. i wish i hadn't taken the bed panels i had in loose, but at least i learned a little.