Just to ease my mind- TO-20

Friend has a TO-20 that did run well but now is giving him fits. He got a set of points, a 2 piece type, and installed them as he had been having spark issues. They melted. The plastic parts on the points melted, the spring turned blue, etc. The faces of the points themselves looked almost new with some very slight pitting. My first thought was that he should have a 12-6v resistor in the line ahead of the coil. He doesn't think so because it ran good for him before. I checked the new points to see if there were any grounding arc marks visible and can't see anything, and there was no apparent grounding or anything around the stud through the distributor wall. I'm not a Fergy guy, but I'm pretty sure these were 6v to start with and he's got a 12 v batt in there. They were negative ground? That's how it's set up now on the wiring and at the coil. My best guess is that the coil needs that resistor to start with.

I'm just wondering if there's some well known cause for this specific to Fergusons that I've never heard of that everyone else knows about. Seems like a long shot but I thought I'd ask. Doesn't seem likely that they are any different than any other ignition system of that era. Lord knows what kind of coil is on it as he got it from a junky. I also noticed the distributor bushing/bearing is growling very noticeably and the shaft has a good 1/8" of sideways play in it if you push it around. Nice old tractor though.

The loose distributor may be why the points went, and yes there should be a resistor from the 12 volt to 6 volt coil. If your friend wants, all of
the parts are here on the parts link. I would buy the 12 volt coil instead of the resistor and there is also a bushing kit for the distributor

Keep us posted

Finding 1/8" slop in the distributor shaft is most likely the root of the problem. That will have to be addressed first. With that much wear, it is probably not going to be practical to repair, but won't know until it's apart. A rebuilt distributor is available on this site. Be sure to check the number of teeth on the gear, put the wrong one in and it will ruin the cam!

You can check the coil with an ohm meter. A 12v coil that does not need a resistor will have about 3 ohm resistance across the primary terminals, a coil that needs a resistor will have about 1.5 ohm.

Might take a look at the wiring. Look for crumbling insulation, mouse chewing, loose or corroded connections, and be sure the ignition switch delivers full, steady voltage each time it is turned on.

Thanks guys.