12v coil...need a resistor?

I recently swapped my 52 8n 6v generator, coil and voltage regulator with a 12v gen/coil/vr.

Do I need a ballast resistor if I'm using a a newer 12v coil with my original distributor and points? I'm not having any problems, but someone mentioned to me that I'd eventually burn up my points. I thought that was only if I used the original 6v coil without a resistor.

Thanks,
Dave

First, if you canabalized an automotive twelve volt system for the parts go back to the same system and get the balast resistor to match the coil. If you bought a coil over the parts counter go get the parts person to find a resistor to match. If you have a coil that needs a resistor and you run it without one it will last maybe as long as ten hours before it turns to toast.

Next guess--if you grabbed a generator off something like a V 8 Chev check the pulley sizes against the flathead. On a V 8 the pulleys will be sized to not over speed it at five thousand engine rpm which will result in little or no charge at tractor engine speeds.

Or just go in and fix the trouble that caused you to start converting. Neither of my six volt 8N's missed a start last winter in Montana. You can do a six volt tune up--new two gauge cables, wiring harnass, generator rebuild, wire brush the connections--and have money left over before you even pay for a twelve volt battery let alone the conversion parts.

Your mileage may vary

-The 12v coil was one I had on the shelf.
-The generator came from a chevy 235 6 cyl.and charges fine on the tractor (although throttle has to be nearly full).
-I have no $$$ into this conversion. Even had the battery on hand. I can burn up five sets of points before I spend the money a new 6v battery would have cost me.

Just funnin. I do appreciate the response.
DaveG.

When you post trouble questions--and I would bet you are going to have them--post what type of twelve volt system you have cause most folks are going to assume an alternator and other things that don't apply.

You could fiddle with pulley size on that generator to get more kick at idle but may not be worth the trouble if you battery is staying up.

Your mileage may vary

Some are designed for true 12 volt operation, no resistor needed. Some are designed for ballasted 12 volt operation. If'n designed for ballasted operation, it needs a ballast resistor, plain and simple. And donna ask me what value ballast resistor to use, cuz its a deep dark secret, known only to yer parts person.

I flunked mind reading, just ask my ex-wife, BUT I'll give ya some ballpark guesstimates...if'n true 12 volter, primary resistance will be about 4-5 ohms. If'n a ballasted 12 volter, primary resistance will be about 2-3 ohms.

And if'n its a true 6 volt coil, primary resistance will be about 2-3 ohms (isn't that interesting? wonder why?). Secondary resistance will be about 5000 to 10000 ohms in all cases, so you should have no doubt which ignition coil winding you are measuring.

You can get a passable volt/ohm meter at yer local mega-hardware warehouse store for $20 cheep or $200 at a highend autoelectronics emporium. Its yer dollar, but you can always use one for trouble shooting.

That said, ohm meters are not too accurate at low ohm reading (has to do with ohm meter design) so if'n ya gotts a 1.5 ohm reading, well guess what, thats close enuff to 2 ohms to be considered a 12 volt ballast required 12 volt coil. OR if'n ya read 5.5 ohms, ya probably gotts a real 12 volt coil. BUT if'n ya reads 3.5 ohms, donna know whats ya gotts, but if'n ya ain't burning ignition points, then ya probably gots a true 12 volt ignition coil and leave it alone.

As one N-Board member likes to point out, there are many ways to convert to 12 volts and some of 'em even work..... ..Dell

Thanks for the reply. I already have a nice multimeter handy, so I'll put it to good use with the information you gave me (which I've saved).

The 12v coil is from an 85 Mazda GLC (had the part on my shelf). Maybe I'll call the parts store and ask their computer if it needs a resistor.

Thanks again,
DaveG.

• wiring diagrams

Great reply!
Thank you for the help. I appreciate the extra effort and the link, too. I've got it bookmarked.

DaveG.