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| | | | Joined: Jul 2007 Posts: 28 'Bolter | | 'Bolter Joined: Jul 2007 Posts: 28 | Hello all.
I recently hit substantial completion on my 1941 3/4T GMC PU but have yet to hook up the original gauges. I may have an issue with the gas tank sending unit. I converted the truck to 12v and have the 6v resistor to place on the hot side of the gauge. However, when I purchased my new gas tank and sending unit, I ordered a 12v sending unit, not knowing the wiring configuration at the time.
Now knowing the sending unit gets its juice from the gauge, it seems the 12v sending unit will not work. Is there an easy solution for this or do I need to purchase a 6v sending unit?
Any comments or help are greatly appreciated.
Thanks, | | | | | Joined: Jan 2022 Posts: 2,476 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,476 | What "12 volt" sending unit did you order? What is the full and empty ohms readings on the sending unit?
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | Sender is not voltage specific. There is no juice to them. Who sold you a "12V" sender? Just need to have a 30 OHM rating,
1. DO NOT run ANY voltage to the sender.
2. GMC's had positive ground.
3. Gauge has two terminals, one for voltage and one for the sender.
4. If you don't know about wiring, seek help here before wiring.
5. On your truck, the fuel gauge "frame" needs to be grounded. Probably has a lug or brass plate to touch dash metal when tightened up,
6. The sender terminal on older Chevy gauges is on the "F" side of gauge and may have a red warning tag.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: Jul 2007 Posts: 28 'Bolter | | 'Bolter Joined: Jul 2007 Posts: 28 | I may be mistaken about the 12V sender. I purchased it from Tanks, Inc. but don't have the model number handy and it is in the tank now. From the comments received, the sender is neither 6v or 12v - just a sender that with an OHM rating. I do recall they asked me about the OHM rating which I gave them at the time - it has been a few years since the transaction so the details are a bit foggy and I can't find the paperwork.
My intent was to connect the sender to the red tag side of the gauge as you noted.
I should have mentioned, I also converted to a negative ground.
the gauge cluster is grounded.
If I understand correctly, the sender has no voltage or juice to it. if the ohm rating is correct, connecting it to the red tagged lug should provide a working gauge.
I appreciate the clarification and direction!
thank, John | | | | | Joined: May 2005 Posts: 8,983 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,983 | Yes sir.  Will provide a working gauge if the gauge is working and the sender is working and grounds are viable. Recommend adding a wire from a sender flange screw to the frame for good ground.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
| | | | | Joined: Jul 2007 Posts: 28 'Bolter | | 'Bolter Joined: Jul 2007 Posts: 28 | Still learning here and all the help is much appreciated. I will add that ground as recommended.
thanks! | | |
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