The Stovebolt Site Forums The Shop Area The Electrical Bay Converting to 12V for starting only

This is probably a dumb question, but I have searched and can't find an answer. So, here goes: I have a 52 Chevy, 1/2 ton with the original wiring, generator, 6V system (although someone converted it to positive ground). I want to keep it 6V because one of the reasons I love my truck is that she is all original. I don't drive her at night, so no worries about dim lights and all that. But, I have a cranking issue. When cold, she spins right over. When hot, she sometimes will barely turn over, and I have to wait for her to cool off before she will crank. I have good, paint-free connections, and am running 00 gauge cables, with a good battery. Old-timers tell me that all these old 6V vehicles were that way. I would love to be able to convert so that I had a 12V battery, and 12V would go straight to the starter. But, I would put a large, ballast resistor to the rest of my electrical system, limiting that to 6V. Now, I assume that would not work because the generator and voltage regulator would only produce/or limit the voltage coming back to the battery to 6V. So, since the battery couldn't charge to 12V, that would negate the entire plan. That is my thinking. However, I have talked to many people who put 8V batteries in 6V systems (I guess an additional 2V won't fry things)and they talk about how much better it cranks. If the only change is dropping in an 8V battery in place of a 6V, then since it only charges to 6V, are they fooling themselves that it cranks better? What am I missing here?

An 8v battery is NOT the way to go. It's a poor "fix" for another problem. Make sure your connections are not only paint free but rust free as well. Good grounds are absolutely necessary with a 6v system. Cranking slowly when hot is a symptom of an issue not yet diagnosed. It's not normal. Hard starting is often normal because of the way the manifolds are designed but slow cranking is not. IF your battery cables are "eat off of" clean, IF your cables are 00, IF your battery is good (what is the CCA rating of your battery anyway?), you need to check your starter. My six volt '38 cranks like a champ when hot.

An additional thought, check your ignition timing. If it's advanced too far it can slow the starter when cranking.

An 8V battery is a solution to a nonexistent problem. It requires the voltage regulator to be adjusted to 9.5 volts to keep it charged, which does fry light bulbs (headlights in particular) and it also seriously shortens ignition point life. These are not just idle opinions- - - -I grew up around the best auto electrical shop in Nashville Tennessee in the 1950's when 6V systems were common. The lazy person's fix back then was a special 12V battery with a series-parallel switch built into the top- - - -essentially two 6V batteries that automatically went into series to provide 12V for starting, then went parallel for running and charging. Those things were P.T. Barnum Specials- - - -and the local Nashville battery company (Hester) that sold them found a huge number of suckers to fleece.

If you've got a hot start problem, either your starting/charging system isn't as well-maintained as you think it is, or the engine has some internal problems that cause it to tighten up when it's hot. After 60-something years of doing (and teaching) automotive electrical work, I'd wager I could find, and probably fix the problem in an afternoon. Where are you in Alabama? I'm about 40 miles northeast of Huntsville, close to Fayetteville Tennessee.
Jerry

I thinks the guys above have it right. The positive ground can be changed to negative ground if you wish. It's not an electrical issue, more of a mine set thing. Hotrod can tell you how to git 'er done in several short sentences.

Well, the thing is that it only had this particular problem two or three times in the past couple of years. Most of the time she spins over and fires right up. I was just thinking of ways to make it never happen again. The battery is over three years old, so that could be part of the problem. But, you have already answered my question...throwing in an 8V battery is not the solution, contrary to what I have heard.

Never heard of someone switching a neg ground system to pos ground. Are you sure it's not a GMC that you think is a Chevy? GMC's had pos ground during early eras.

Read this for change over advice regardless of what you have.
http://www.inliners.org/tech/12v.html

"Old-timers tell me that all these old 6V vehicles were that way."

Those old timers are correct: they were that way because of:

- small gauge cables - especially the ground cable
- bad cable connections - all should be shiny surfaces with copper-impregnated conductive "grease" (NOT dielectric grease)
- weak battery
- starter that needs a rebuild
- poorly tuned engine (especially timing & carburetor)

They did not (do not) have to be that way.

I think Tiny's description is spot on. My stock 6 volt system starts fine.

No, it is a Chevy. But, it DOES have a positive ground. No telling why.

If it was me I'd change it back since all Chevy's were negative ground. It'll help prevent a major FUBAR sometime if someone assumes it's negative ground while working on it.

Switching polarity is easy- - - - -just make sure the (-) side of the coil is connected to the distributor, and repolarize the generator after swapping the battery cables around by touching a jumper wire from the BAT terminal of the regulator to the ARM terminal for about half a second. You'll get a pretty good flash- - - -that's normal.
Jerry

Yes, I have thought about converting it back. I plan to probably have new wiring installed someday. That would probably be a good time to convert it. When I got it I had to reverse the wiring on the blower motor and he ammeter because they were backwards! The fuel gauge didn't work, can't remember if I had to reverse anything when I changed the pickup or not. But, everything seems to work okay how it is, so I believe in leaving well-enough alone. Now, if I could just get her to start reliably when hot.
Thanks for all the inputs. You confirmed what I believed...dropping an 8V battery in is not going to solve the problem. It pretty much has to be that enough current is not getting to my starter, or my starter is getting squirrely. I rebuilt the starter a couple of years ago, put those big cables in, made good connections,etc.. But, might be time to look at all those things again.

Check on the coil polarity- - -it takes approximately 20% more voltage to fire the spark plugs from the ground side, so if the + cable is grounded, the + side of the coil needs to be connected to the distributor. That won't help the cranking speed, but it just might make a hot start easier by firing the plugs more efficiently.
Jerry

I would not wait one more day to change the complete wiring harness. Whoever wired your current setup did not know what they were doing and there may be some dangerous gremlins about to set your truck on fire.
Carl

Well, it is always the simple things...I cranked my truck up this morning and she spun right up and ran like a fine, Swiss watch. I made sure I kept her running until I got her back home. Shut her down and she would just barely turn over. I decided to go ahead and clean all my connections, staring with the battery. When I pulled off the battery cover it hit me. The tag on the battery says it is 4.5 years old!!!! I would have sworn that battery was no more than a couple of years old. Just shows that I am the one getting old. Guess I will get me a new battery. How many CCA do I need? I guess more is better, but no sense in overkill.

That's not old for a good battery. Load test it before assuming it's the problem.