12volt conversion question ballast resistor

[mtd1960]

If I were to run my model A on 12 volt neg ground, would a ballast resistor be needed for the 12v coil, i am running a dist with modern points and cond.
Thanks for the input.

[Jim Johnston]

Auto Zone Duralast Coil P/N LU800 has an internal resistor so you don't have to use an external ballast. NAPA has a similar coil but don't know the P/N.

[Mike V. Florida]

If you were to use the same coil that you were using on 6 volts, yes a resistor would be needed.

[MikeK]

There are advantages to running a coil with an external resistor. The white porcelain/ceramic external resistors are PTC, or Positive Temperature Coefficient resistors. When cold their resistance is lower and you get a hotter spark. In about 10 minutes of running they warm up and the resistance is higher, reducing coil average draw to about 3A. The average draw is a function of dwell.

Most 12V coils that are "internally ballasted" do NOT have a resistor inside. That would just generate useless, damaging heat. Instead, a true "ballast not needed" 12V coil has same number of turns in the primary winding, but a smaller wire (larger wire gauge #) to keep the amperage draw the same. The advantage of a PTC ballast resistor is lost.

If you do use an external resistor, keep in mind they get HOT and must be mounted with no wires touching them and in an airflow area. They will dissipate 30 -40 Watts of heat, as much as a small soldering pencil iron.

In anything electromagnetic, like transformers and motors, the magnetic field strength is a product of amperage x # of winding turns. There is no direct relationship to simple amperage, voltage, or wattage.

[MrTube]

Wouldn't it make more sense to use a toggle switch to bypass a standard resistor for hotter spark while starting?

Wasting 30-40 watts in heat sounds pretty pointless especially when that extra power could go towards lighting.

[Jim/GA]

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Originally Posted by MrTube

Wouldn't it make more sense to use a toggle switch to bypass a standard resistor for hotter spark while starting?

Yes, this was done on many cars for many years. For example, my '63 Riviera bypasses the resistor wire to the coil when cranking. The idea is that the load on the starter motor will pull the voltage to the coil down when turning over that big, high-compression V8 engine, so you don't want the resistor pulling it down further.

I really don't think you need to worry about this on an A that is converted to 12 volts, as long as the electrical connections are all good and the battery is good. The voltage will not drop that much. If I did it, I would use a push button momentary contact switch to bypass the resistor so that it did not accidentally get left on and burn out the coil with too many volts.

[steve s]

Originally Posted by Jim/TX/GA

... I would use a push button momentary contact switch to bypass the resistor so that it did not accidentally get left on and burn out the coil with too many volts.

How many hands do you have?

[Matt L]

Guys, I am new to Model A's and I got my wife's grandfathers 1930 fordor town sedan. I got it running and took for a test drive and was hit. now I am rebuilding the car and want to update the lights for safety reasons. I am wanting to go with a 12 volt neg ground system and have read many post on how to do this but not 100% sure on points and condenser. If I have 12 volt battery, alt and 12 volt coil all wired properly do I need any thing in line between coil and points? They don't offer 12 volt points and condenser that I have found but I could be over looking them. Any help would be great. Thanks

[Mike V. Florida]

Originally Posted by Matt L

Guys, I am new to Model A's and I got my wife's grandfathers 1930 fordor town sedan. I got it running and took for a test drive and was hit. now I am rebuilding the car and want to update the lights for safety reasons. I am wanting to go with a 12 volt neg ground system and have read many post on how to do this but not 100% sure on points and condenser. If I have 12 volt battery, alt and 12 volt coil all wired properly do I need any thing in line between coil and points? They don't offer 12 volt points and condenser that I have found but I could be over looking them. Any help would be great. Thanks

Those that have heard this before, get ready to moan;

If you were to properly restore the headlight system with the properly shaped reflectors and good contacts you will have bright headlamps.

If you insist on spending your money for 12 volts, (you will still need the proper reflectors for good headlights) you need to find out if the coil has an internal resistor. If yes you are set to go, if no then you need a ballast resistor. There are no special points or condenser for 12 volts.

What are you going to do for the horn, re-wire or resistor?
How about the starter, many leave it wired for 6 volts, others have it rewired for 12 volts.

[Jim Parker Toronto]

"How about the starter, many leave it wired for 6 volts, others have it rewired for 12 volts." I did this to my car (left it 6v) and pulled the ring gear off a few times, want to go through all that work to repair that??

[Mike V. Florida]

Originally Posted by Jim Parker Toronto

"How about the starter, many leave it wired for 6 volts, others have it rewired for 12 volts." I did this to my car (left it 6v) and pulled the ring gear off a few times, want to go through all that work to repair that??

Many have left it 6 volts with no problem, many have had it rewired. You're mileage may vary.

[jrelliott]

I have a list of all the bulbs both 6V and 12V for the Model A and an electrical parts chart. If you are interested please send me an email [email protected] and will send them to you. If you do go to 12V, consider putting on a modern barrel drive starter bendix, less chance of breaking off a bolt on the old spring type bendix. Converted mine back to 6V from 12V since getting the electric wiper motor rebuilt, and finding the correct Power House Generator.

[Purdy Swoft]

Here we go again!!!The best and easiest way to go with the coil is to use a coil that is rated at 3.0 OHM. With a 3.0 ohm coil you won't need a resistor because the resistor is built in. Coils are no longer refered to by voltage but by OHM . If you go 12 volt negative ground you will need to reverse the wires behind the ammeter and at the coil, connect the battery negative ground and thats it for the wiring. The halogen bulbs that fit original sockets are mostly 35 watt. If the reflectors are correct they will be bright and should focus. I bought a set of reflectors that didn't have the correct shape and could not be focused so I don't recommend that setup. If you want the brightest focused headlamps use the quartz halogen kit from Brattons. This kit is complete with reflectors and are 60/55 watt and are as bright as modern car headlamps. The part number for this 12 volt kit is 17850 the price is $97.00 and is on page 79 of the currant Brattons catalog. You will need the 60 amp alternator for this setup The starter will work fine on 12 volts with no mods. If the ring gear on the flywheel or the starter drive is worn out it will sooner or later give problems no matter what the voltage. I do recommend and use the new barrel starter drive because it has no bolts that will drop off in the flywheel housing like the old bendix drive. As for points and condenser, they don't know the difference in voltage and will work with six or twelve volt. I recommend the original style points and condenser. I had nothing but problems with the MAKE SHIFT V8 points setup. So much trouble that If I had to use the V8 points setup I would quit the hobby. Some are willing to spend over twice as much for a better brand of V8 points. The way that I see it is there is no advantage with the V8 set up and they are a real pain in the @$$ to adjust.

The same headlamp setup is available in six volt and there is a six voit 60 alternator. With 12 volts you have power to spare. A slightly weak 6 volt battery usually won't have the power to spin the starter and fire the points at the same time. Its your car and your money. This is what has worked for me.

[jackson32]

I had a 8N ford tractor and I put a 6 volt altinator on it it started great because battery was always up and I didn't need 12 volts but the last A rodster I had came with 12 volt system and I had starter changed to 12 volts made things better.

[QGolden]

Originally Posted by jackson32

I had a 8N ford tractor and I put a 6 volt altinator on it it started great because battery was always up and I didn't need 12 volts but the last A rodster I had came with 12 volt system and I had starter changed to 12 volts made things better.

?? The 8N is a 6 volt system.

[jackson32]

Auto electric syastems evolved from 1955 that was 12 volts in gm but they still had generators and voltage regulators even the first altinators had regulators and it was not till around the 1970 ford had a solid state regulator and I dont remember when the altinators were all solid state that when low batteries stoped for good 12 volts did not do it by it self 12 volts with a generator is not better than 6 volts with a generator. You should have been there

[Purdy Swoft]

I had a 55 Ford that I ran 12 volts in 1963. A lot of my friends thought it was a good improvement I still do. We used the 6 volt starter with no modification and never a problem. They cranked a whole lot better and quicker. There was no problem with the larger gauge wire, it carried 12 volts well. I counted off cells on top of the the tar top battery and installed a self threading type screw into the plates . I ran a wire from this screw to the radio. this rig gave six volts instead of twelve so as not to ruin the good radio. I changed out the bulbs. this was a popular thing and had been done for years. It was the older guys that showed me this stuff when I was a teenager.. I'm running our roadster 12 volt with the original generator and love it . I've had no problems with the roadster since it was done in 06. Low amperage high volt doesn't create heat the same as high amp low voltage. I grew up when cars were mostly all six volt and I remember lots of problems. parking on a hill was common so you could roll off to crank in cold weather . Eight cylinder engines could crank on six volt but I've seen lots of them that sometimes wouldn't crank. The batteries would run down pretty quick if many mistakes were made trying to crank them. ights were dim unless you ran an eight volt battery. We just don't see much of this stuff on cars with 12 volt. I remember that the headlights were brighter and they started quicker on even the first 12 volt cars with generators. I really prefer generators but realize that in some cases an alternator is the practical way to go . Twelve volts is certainly not a sin in any case.

[CarlG]

I did pretty much the same as Purdy did on my 54 Ford (in the early 60's). Made it possible to run an aftermarket 12 volt A/C unit I bought from Sears. (I lived in Phoenix then) I always thought that tapping the battery at the half way mark to get 6volts was my invention. (Guess not!) I did use a 12volt Motorola alternator.

[Purdy Swoft]

A lot of the things that were known and practiced by some of us shade tree mechanics back then has nearly been lost in time. Thanks, Carl , for shareing !!!!!!!

[BILL WILLIAMSON]

Originally Posted by CarlG

I did pretty much the same as Purdy did on my 54 Ford (in the early 60's). Made it possible to run an aftermarket 12 volt A/C unit I bought from Sears. (I lived in Phoenix then) I always thought that tapping the battery at the half way mark to get 6volts was my invention. (Guess not!) I did use a 12volt Motorola alternator.

Carl, In the late '50's, we'd take a 12 volt battry with external cell connector straps to Jorgensen Battery, & he'd pour us a post on the center strap to run all our 6 volt stuff. The shop's still operating, through 3 generations of the same family, same building! Bill W.