JD 6V vs 12V Battery – Advice Needed

[ShaneR]

Hi Team,

I understand that my JD was originally a 6-volt system.

From what I’ve gathered, during the later years of its use, it became difficult to start. To compensate, a 12-volt battery was installed instead.

Would running a 12-volt battery on a 6-volt system have caused any damage?

Looking ahead, should I continue using the 12-volt setup, convert it back to 6 volts, or consider installing a proper 12-volt conversion kit?

Appreciate any advice or insights.

[dtoots1]

Bestchoice in using 6 volt starter on `12 volt system...electric motor shop can convert the 6 volt starter to 12 volt....this saves the nose cone from shattering...which does NOT always happen...but when it does...those are hard to come by...my 6 volt system on wheeled jd40s starts winter and summer...long as battery charge good...and blamed thing has good ground...that starter is the kind that has the single cone shaped allen head with lock nut on it...and starter itself needs good contact for ground...somehow where it sets in bellhousing those edges get rusty and loose contact...and bendix will usually get hung up halfway

[fundytides]

I have a 40c and my son-in-law has an MT, both with original 6 volt systems. Both machines will start quickly and easily as long as points, condenser, etc. are in good shape and the battery and starter have a good ground. Usually 12 volt batteries were installed to compensate for problems in the rest of the system. To me money is better spent bringing the 6 volt system up to par rather than coverting everything over to 12 volt. Just throwing a 12 volt battery in does not resolve the real issues and may cause other problems, like shattering the starter "cone" as pointed out by dtoots1. I also have a Model T Ford and a Model A Ford with original 6 volt systems that don't give any problem if properly maintained. When I was growing up, here in New Brunswick in the 1950's, I had a lot of cars with 6 volt systems. Even with temperatures commonly dropping below 0 degrees in the winter, these cars would usually start well with the exception of my 46 Nash but it had a worn out motor with low compression and was hard to start on cold days with a 12 volt boost. Just my 2 cents worth.

[Stan Disbrow]

Hi,

Well, 12v on the 6v starter is Bad News, as already pointed out. But, there are 12v field coils and armatures to correct that.

Then the coil is wrong, but a ballast resistor fixes that. Or, some folks use a 12v coil.

Just changing to a 12v generator isn't quite enough, changing the voltage regulator is also required. But, most install a one wire alternator, so just unhooking the original regulator is good enough.

The points can give trouble. The metals used are reversed on 6v points v 12v ones - not due to the voltage, but due to the polarity difference. 12v being negative ground and 6v being positive ground. I would use an electronic module to have the points fire the coil via that.

I will add to the thought that a 6v system where all the connections are decent does not give trouble. I have had plenty of them although only one remains today. A 1950 Model M and it is still all original. The ignition switch is becoming a bit fussy to make in the Low Charge position, but using the High Charge is still OK.

The M has a 3-brush generator, so no regulator, and you choose using the two positions on the switch. Later machines had a more powerful two-brush generator and so sported a regulator and three lights vs only two on the M. They have what we refer to as an ILBD switch.

Stan

[ShaneR]

I would use an electronic module to have the points fire the coil via that.

12 volt or 6 volt?

Are they easy to get?

[Lavoy]

Currently 12 volts fields are somewhere between difficult, and impossible to get. Hope it changes in the future, but I doubt anything in the short term.
Yes, 12 volts on a 6 volt starter is eventually going to break the starter nose cone, and/or the ring gear. Your current 12 volts was a bandaid fix for an underlying problem.
6 volt parts and rebuilt starters are not an issue, I have most of that on hand. I have new generators on hand if yours is not rebuildable, but doubt that is the case.
Other than likely starter issues, the other problem that many people experience on 6 volts is they buy the cheapest POS batter they can get. But a good 600CCA 6 volt battery, fix any underlying issues in the system, and I start them during the winter without issue.
If you want to rebuild your starter, I do have a few high torque 6-volt fields on hand.
Lavoy

[Stan Disbrow]

Hi,

The electronic control modules for 12v point systems are common enough. The 6v ones used to be but pretty much disappeared as new in the 80s. They were a favorite with the older Volkswagon crowd, but those as 6v had dwindled down by the 1980s. Probably need a car show swap meet to find one these days.

I would not bother with one on a 6v system, but would want to use one on a 12v conversion - if I ever did one.

I have always done well keeping the 6v systems operating. As Lavoy pointed out, a good battery and the proper size cable pretty much does the trick. I did have one machine, one time, where the electrical ground from the dashboard to the engine block was iffy. I opted to run a positive ground cable from the battery to the starter mounting bolt directly and that fixed that.

Stan