I’ve got a 1950 GMC that was a 6 volt positive ground system. I’ve read lots of tech articles about converting to a 12 volt negative ground system, but nothing about just switching from 6 volt positive, to 6 volt negative. I’m trying to restore the truck to original, and was trying to keep it 6 volt positive ground. I’ve been successful up to this point, with the truck starting and running good on 6 volt positive ground. The issue started when I ordered a new fuel gauge from the normal vendors. I ordered the correct “GMC only” fuel gauge, but was unsuccessful in getting it to read correctly (all grounds and wiring are correct).
I called the vendor, who in turn call the manufacturer of the gauge, and they specifically said it would not read correctly with positive ground. I then removed my battery and sending unit from the truck, and performed a bench test using negative ground, and it the gauge read correctly and flawlessly. I am now at the point where I need to decide to try and find a fuel gauge that will work with positive ground, or switch the entire truck to negative ground.
So my main question is, can I simply just switch the + and - leads on the battery, and everything will work correctly, or are there other things I need to consider? The truck is already all wired for 6 volt, and I’d like to keep it that way. I just need to know if the regulator will be ok with the polarity switch? I know the starter won’t matter, and I may need to switch the coil leads around, but my main question is about the regulator. The only other circuit on the truck is the lights. No radio or other accessories. Can I just the swap connections at the battery?
Martin '62 Chevy C-10 Stepside Shortbed (Restomod in progress) '47 Chevy 3100 5 Window (long term project) ‘65 Chevy Biscayne (Emily) ‘39 Dodge Business Coupe (Clarence) “I fought the law and the law won" now I are a retired one! Support those brave men/women who stand the "Thin Blue Line"! Hug a cop! USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
hi JakeM, i would encourage you to pursue keeping your truck original and finding a better gauge or fixing an original one. they are only original once
I have not tried swapping the fuel gauge, but i have fixed them and studied their design, from what i can tell an OEM fuel gauge should work either polarity. So the aftermarket one you got is doing something more modern inside if it can't work for your situation. The OEM design is two electro-magnets in a balancing act, swapping polarity swaps both the magnets, they should still perform the same balancing act unless something less intuitive is going on that i'm not seeing at the moment. best of luck -s
Converting to negative ground is easy- - - -but it's a cop-out to keep from correcting the problem that exists, caused by the gauge manufacturer. If you decide to take the easy way out, simply reverse the primary wires at the coil, swapping the position of the wires from the ignition switch and the distributor with each other, switch the battery terminals, and repolarize the generator for negative ground. The starter, lights, and other gauges don't care what the polarity is. If the ammeter reads backwards after the polarity change, just swap the wires at the back of the gauge, but I don't think that will be necessary. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Jerry, thanks for the info. I figured that was what I would need to do, I just needed confirmation. I would really like to keep it positive ground, but all of the vendors sell the same reproduction gauges from the same manufacturer. The original gauge is unusable. I finally had a vendor today call the manufacturer, and they told them to tell me that no one makes a positive ground gauge any more. I’ve been fighting this battle for about a month now with them. The truck runs and drives great on 6 volt positive ground, and that was my intention all along to keep it that way. I really don’t want to swap it over based only for the fuel gauge, but I may not have a choice.
There might be a way to insulate the gauge assembly from the dash with some creative use of paper or plastic gaskets, and apply the wire from the ignition switch to the part of the gauge that would normally be grounded to the dash. Then reverse the wires that would be attached to the sending unit and the insulated post where the ignition voltage would be applied. When I was driving an old Freightliner with a positive ground system, I wired up a radio that way, using a wooden box to keep the radio case from getting grounded and running the power wire to the case. Worked great! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I found my Delco Remy manual, and it turns out they are polarity sensitive (at least my series of regulator is). Apparently it’s pretty easy to tell, it’s stamped right on the base of the regulator. See attachments.
Now I’m left with either trying to find a positive ground fuel gauge, or funding a Chevy negative ground regulator and swapping the entire truck to negative ground. I’m sure the Chevy regulators are easy to come by, but I really didn’t want to go that route.
Running a positive ground regulator on a negative ground system doesn't create any catastrophic failures- - - -it just doesn't last as long because of the potential for metal transfer from one vibrating point to the other on the voltage control unit. The current regulator and cutout relay won't be affected either way. At least that's what a Delco-Remy instructor in a seminar I attended back in the early 1960's told us, and 50-something years of servicing DC electrical systems has proved to me that it's true.
"Your mileage may vary"!
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Looking through my parts pile, I found an old Sorensen voltage regulator. I may give that a try. It’s says on the cover “6 Volt- Negative Ground”. Looks to be serviceable.
Good luck- - - -there are two kinds of voltage regulators for GM vehicles- - - -"Delco-Remy" and "wrong"! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The voice of experience isn't always sugar-coated! I wear the "old coot" label with pride! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
