My son bought a 1952 Buick Special that the previous owner changed the ignition and engine to 12 volt. I'm trying to convert the rest of the electric to 12 volt negative ground, the issue is my son won't let me change the wiring harness ( I figured get a modern fuse box and new wires and rewire the car) but he wants to keep the original wiring. Problem is I'm finding wires that should be positive carrying a negative charge and vise versa....I'm starting to pull what's left of my hair out....I don't want to just connect the 12 volt to the fuse block and see the fireworks... Am I thinking on the right lines, take each individual system ( headlight, taillight circut, Horn circut, turn signal circut) disconnect everything in the circut and trace each wire and do proper connections?? I found out the hard way, them freaking horns are loud as hell!!! Still can't hear right in my left ear, testing circuts with a test light and accidentally touch 2 terminals at the same time and them horns went off and I about jumped out of my skin...lol Any advice on converting this would be appreciated!! I do have the resistors for the gauges and radio
I'd start with a diagram and trace wires to the different circuits. Then you would be able to repair/replace anything that needs it and know how it's supposed to be. Good luck!
That car is, and always was neg ground. If the wiring was original, converting is simple. With what you are saying you found, maybe not so. I changed all the light bulbs. Installed a resistor for the gas gauge. As I am using an 85 amp alternator, I bypassed the amp meter by moving the incoming wire to the same post as the outgoing. I use a Volt meter. Left radio and heater unplugged. If using a later 12V generator, hook it up as the original. If going to an alternator, which I recommend, simply bypass the voltage regulator, connecting the alternator output to the battery post on the regulator. I actually hooked the wire that was hooked to the Bat post on the regulator directly to the alternator. I am using a Delco 1 wire alternator. I used a coil that does not require a resistor. The starter will work for a long time on 12V. Mine eventually shredded the drive [ bendix ] gear. I then replaced it with a 12V Mini. Happy. The 6V wire is heaver than needed for 12V , so good to go. If you use an alternator, the starter relay will need to be grounded if it is like 1950. That should about do it, I think. As for changing the fuse box? I wish I had done so. Ben
Sorry, but I’ve got to ask. What kind of shape is the original wiring in. Almost every 50’s car I’ve worked on is brittle and cracking, even the older fabric or rubber wiring is falling apart. Terminals corroding, or wiring fraying. Is it that important to keep the original? Sounds like it’s asking for problems to me. And some of those problems result in fires.
I have to agree. What's the point of keeping a 75 year old wiring harness? Even if it was garage kept all it's life, fabric or rubber insulation is gonna break down after 3/4 of a century! $250 will get you a new harness, fusebox, etc. Seems like a no brainer to me.
He wants to keep 72 year old wiring? I would have already gutted the entire harness, it doesn't last forever and I can already imagine what that old cloth covered wire looks like, especially in the engine compartment. No one looking at it will care that it isn't original. If it needs to look the part, American Auto Wire sells a nice cloth covered harness...at a premium price. Buick may have had an engine named the Fireball, but that doesn't mean the rest of the car should be called one.
Everything on the car is in surprisingly great shape! When we changed out the 6 volt headlights to the 12 volt, the wires at the connector looked brand new...
Oh I'm still trying to talk him into a Painless or Francis wire harness and fuse block, I think it would be easier.
The previous owner told me it was positive ground......after I saw your post I checked the buick shop manual and you're correct.....which kinda scares me, if the P.O. thought it was positive ground, and I'm finding negative where it should be positive....oooooh boy, it's gonna be easier to just replace the harness instead of tracking everything down....
If you’re going to lose that battle, buy one of these. The big ones are easier to read and well worth a few bucks more. https://classiccarwiring.com/products/1951-1952-buick-series-40-50-70-color-wiring-diagram
Those Classic car wiring diagrams are nice, I have one for my 71 GMC and it is laminated and poster size. Worthy of being framed and hung in the man cave if you don't need it pinned to the wall in the shop next to the ride it is for. 72 year old wiring is freaking scary and about the second wiring bonfire he will be thinking different on that although lamely blaiming it on 12 volt rather than old bad wires. My 51 Merc was 12 years old when I bought it and the fabric covered wiring was already shot.
It sounds like you've got a real mess on your hands. I'd start over. If you want the look of original wiring, you can get a harness from places like Rhode Island Wiring for most cars that age, or buy a couple spools of linen wrapped wiring and make your own. Without seeing it, it's hard to believe the original wiring is as good as you say it is, as it breaks down with age no matter how it's been stored.
Save your self a lot of head aches, and put a new harness in the car. I used a Kwik Wire harness in my 49 Buick. Replaced the Amp meter movement with a volt meter and kept the same gauge face. Now straight up is 12 volts, to the right is more than 12 volt, and to the left is less than 12 volts. If you click on the the bottom link it will show how to build a voltage regulator for your 6 volt dash gauges to run on 12 volts. I did this for my gas gauge and it works great.
I am planning on using Kwik Wire on my 50. Do you have a link or any detail on that volt meter conversion?
I just found a small volt meter that had about the same needle sweep as the stock Amp gauge. Took the movement out of the case and figured out how to mount it in place of the stock Amp gauge. It was pretty easy once I got started. You just want to use a gauge that has 12 volts in the top center of the gauge so the Dis and Chg makes sense when you read the gauge. Been working fine for about 8 years now.
A new reproduction wiring harness is available. That keeps everything looking 100% as original, with correct factory cotton covered cables and correct color codes. Harness made for six volts is perfectly suitable for 12 volts. Needs a 12 to 6volt regulator for the fuel gauge, not a resistor. Remember, the only item on the car than can destroy the car when it fails is the old wiring. Think about it.
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