MTFCA Forum

Is it a good idea to convert my starter to 12v? Where do I find instructions on how to do it?

Ahh! It has been done more than once.

I believe it has to do with joining the field loops (??) up in a different order...

It has been explained to me twice but I still did not get it.. but you can start by looking here: http://www.mtfca.com/discus/messages/80 ... 82269.html

David- it's not a good idea to convert to 12 volts. Why are you considering this?

I lean toward an 8v battery. No other changes to other stuff needed. This may be a patch to cover the real problem(s). If you feel your starter @ 6v isnt cranking fast enough, you may have power connection or weak starter issues. Fit them first. A stock low compression T will work fine @ 6v. Test for voltage drops & proper heavy battery cable.

You'll probably save time and money by finding out why your T won't start reliably on 6 volts and correcting the problem. I've had a lot of vehicles with 6 volt systems, including a Model T, and they work very well in any weather as long as they are in good condition. They're subject to the same issues as 12 volts systems, no more, no less. 6 volt systems are NOT less powerful than 12 volt systems, provided that both are in the same state of repair.

I should have provided more info.
Starting is not a problem. The car has a 12v. battery, 12v. coil & distributor, headlights etc.
High compression head.
I want to lessen the stress on the Bendix, ring gear etc.

Thanks,
Dave

I'm not sure that converting to 12 V will "lessen the stress" on the starter or ring gear. The only major advantage of a 12 V system is that by doubling the voltage, you reduce the current by 1/2. This allows smaller wire and cable sizes. It will still take the same number of electrons to turn the starter under the same load.

If you are dead set on a 12v starter, get one of those new ones made for 12v. $400+. They seem to work real good, according to guys i have talked to. Keep the left hood side down. They are bat ugly wrong. Thats the trade off.

Bat ugly? Awww..... I think the new starters are elegant.

If this sounds familiar we just had a similar discussion on another thread.

I also have a high compression head and originally ran a 6 volt starter on 12 volts. To drop the voltage a bit I put the battery in the back seat, ran #4 wire and put an old bendix spring in series with the cable from the solenoid (yes, I used a solenoid, not a foot switch) to the starter. Normally it worked fine but a couple of times I stalled out on tour (engine hot) and had to crank it by hand beyond compression before the engine would turn over. I also had a bendix problem (slipped woodruff key) another time. These little things bothered me enough that I decided to purchase a modern starter designed for the job. I wanted to stay with 12 volts for a number of reasons which need not be discussed now.

I took my 6 volt starter and the diagram for re-wiring it for 12 volts to a reputable old-time auto electric shop. When I explained what I was thinking and showed the guy the starter his reply was "Aw....you don't want to do that....." Indeed, he refused to do the mod. I'll leave it to others to debate the pros and cons of that modification. At that point, I decided to look at a modern replacement.

The WOSP unit is a geared starter, with a built in solenoid. You can keep your foot switch, just use it to activate the solenoid. When activated, the starter gear first engages the flywheel, then turns. Less wear and tear on the gear teeth. Also, no little bendix parts to come loose and end up in the engine. In the year I've had the starter it has worked well and given me zero problems.

They aren't cheap, but I covered most of the cost by selling my six volt starter and bendix. My goal has always been to have a reliable car for touring and the starter goes a long ways towards meeting that goal. If a future owner wants to return it to original, it is a simple matter of out with the new and in with the old.

Hi Dave,
The info you are looking for is in a post from AdminJeff on Feb 02 2020 pictures & diagram.
My Brother in law took his to a generator shop they did it for $40 it works great. One of the local club members is doing it also.
Craig.

David- it's not a good idea to convert to 12 volts. Why are you considering this?

Well, I think its a great idea. Why?
1) 12v batteries are much cheaper and
2) 12v batteries are much easier to get these days (at least where I live)
3) a 12v system gives brighter lights (read safer driving) (note: it is illegal where I live to put in LED bulbs unless originally installed by the manufacturer - go figure that!! - and this isn't California either.)
4) car runs way better on "BATT" under 12v than 6v (my mag has died)

"Its not original"
"Henry meant it to be 6 v"
"No need"

Nothing intrinsically wrong with 6v starter system either. If it is set up right, and if you can afford 6v batteries and can get them easily then stay with 6v.

Otherwise, well, if it works for you, then it works.

To convert the stock 6 volt starter to 12 volts requires rewiring the field coils from parallel to series.

Craig Leach wrote: ↑

Thu May 06, 2021 11:41 am

Hi Dave,
The info you are looking for is in a post from AdminJeff on Feb 02 2020 pictures & diagram.
My Brother in law took his to a generator shop they did it for $40 it works great. One of the local club members is doing it also.
Craig.

I'm moving to Idaho in 10 days so my entire shop is in boxes (the new shop is coming along great!), however, I did document this entire process. I and others with similar skills have done several of these conversions and they work really well.

viewtopic.php?f=2&t=10169

Just for the record - The 12V battery that I bought at Auto Zone for my '05 Dodge cost $173.95; The 6V battery that I bought for the T in the same store cost $91.49. How does converting to 12V save money?

Adrian, it's probably a response to the fact that LED bulbs cannot be focused or directed satisfactorily to avoid excess glare for oncoming traffic. LED's require specifically designed reflectors.

Allan from down under.

Just for the record - The 12V battery that I bought at Auto Zone for my '05 Dodge cost $173.95; The 6V battery that I bought for the T in the same store cost $91.49. How does converting to 12V save money?

Thats GREAT news for you guys. Sadly for me here its like about $120 (or sometime less) for a low cost but OK 12V battery and easily $400 (often $600) or more for a 6V. Different markets I guess.

Adrian, it's probably a response to the fact that LED bulbs cannot be focused or directed satisfactorily to avoid excess glare for oncoming traffic. LED's require specifically designed reflectors.

Chatting to a friend who is a vehicle inspector it has more to do with 'boy racers' putting fancy bulbs in their 'rice rocket' cars to see how many other Japanese cars they can melt on the road !

Reflectors can be an issue, but is not such a biggie when the bulb is carefully selected, however, our bureaucrats decided it was easier to decide that one rule will be made to fit all...

Harbor Freight battery cables?