Super-A points melting

I have a '49 Super-A, 12-volt system with a one-wire alternator and a distributor. I have been running it flawlessly for about 20 years, but now I've developed a problem with the plastic extension of the points, that run on the cam in the distributor, melting, which kills the gap and the engine, and it happens within 200 yards of driving the tractor. I'm trying to intuit what would be causing so much excess power that it would be melting the plastic. So before I start taking things apart and fishing for an answer to something I don't understand, I am asking if anyone might have an opinion, or have experienced something similar.

I've asked plenty of people in my area, but everyone seems stumped. One guy said I needed to replace my distributor cap, but that didn't make sense to me. Another said it could be a bad condenser, but I replaced that along with a new set of points, and the problem persisted. Another guy said I needed to put in a ballast resistor and step it down to 6 volts, and I could see how that would spare the points from melting, but it wouldn't answer why this thing has run so well for so long, nor get to the root of the problem. Yet another thought I had gotten grease on the points, that something might be 'arcing'. After all that, I've gone through 4 sets of points with no improvement (though I did not put in a ballast resistor).

I would think a 'short' somewhere would kill power, not increase it. The only other thing of which I can think is that there is a corroded wire somewhere, and the resistance is causing the alternator to make more power than needed. Is that logical?

I'd love to hear any thoughts, advice, or experiences. Thanks.
 
Seen that many times on points made in the land of almost right. So where are you buying your points at?? If TSC well there is the problem. Now if you do have a true 6 volt coil and no ballast resister the coil many be going bad which can also cause that. Also now days one has a 50/50 chance condensers are bad right out of the box. I my self have not changed a condenser in over a decade in any of my tractors
 
Alternator would not cause that problem unless the battery was disconnected since the battery will limit how many volts the point will see
 
I have a twelve-volt coil and no external ballast resistor. Never had one, and it ran fine for two decades. Would a bad coil increase power? (And I am making an assumption, that it is actually too much power that is making the points-plastic melt).


And I hear you about points being made more cheaply. My father-in-law, twice, on his 450, had the metal leaf-spring on his points crack and split, which of course leaves the points dangling with no tension. Never had I EVER seen one of those break, let alone twice in one year.
 
I would measure the primary current.

3-4 Amps is reasonable, over that you get excessive point and coil heating. Perhaps some turns have shorted in the primary winding of the coil, increasing primary current draw.

Also (at least the past), quality points typically had a phenolic wear block, tougher and more resistant to melting that the cheap thermoplastic wear blocks on cheap points.

Also, are you SURE they are melting, or is it possible there's some rough rust on the breaker cam that's abrading them away?
 
Warren, I saw Old's reply, but maybe I'll do it just for the practice. Assuming I'm measuring volts, hould it not be making 13-14 volts, no, so it can be charging the battery? SOMEWHERE, it seems to me, the power is getting seriously stepped-up.

I have another set of points, and if I'm going to be testing circuits, I need to have an organized plan of testing before I burn this set too, or I'll be stuck until I can buy another set.
 
Bob. appreciate yours, and everyone's input. I can measure the amperage. Forgive an electronics rube, but should I measure that at the alternator? Because it seems to me there's no where else where amperage would get increased.


I have no way to add pictures here, but they all have a blob of plastic attached to, and downhill, from the block, as though they were melting toward the points themselves.
 
Most 12 volt conversions did not include changing stuff in distributer to 12 volt. Just put on a resister that reduces 12 volts to 6 for the distributer itself. If this is what happened with your 12 volt conversion, then you need one if it don't have one, and if it has one it could possibly be bad.
Why does it do it now, and not before?? That's puzzeling. Did you recently change points or anything when trouble started? Like put on some 6 volt stuff when equiped for 12. The only thing else I can think of, is maybe it was ran with an improper system long enough that some how the coil or condenser is messing up.
 
A coil that has an internal short could cause the points o go bad faster then they should. As will a bad condenser. The condenser is to act as a buffer for the points so they do not spark much
 
(quoted from post at 13:51:06 11/04/18) Bob. appreciate yours, and everyone's input. I can measure the amperage. Forgive an electronics rube, but should I measure that at the alternator? Because it seems to me there's no where else where amperage would get increased.


I have no way to add pictures here, but they all have a blob of plastic attached to, and downhill, from the block, as though they were melting toward the points themselves.


Check the current draw anywhere in the primary ignition circuit, from the ignition switch, to the coil, to the distributor.
 
Good quality points do not use plastic but use a harder piece of what ever it is and it will not melt. I don't think I even have any points in any of my tractor that use plastic on the points
 

If I understand correctly, you stated the plastic running on the cam is melting. Is it possible you have a dry bearing in the distributor that is heating the cam. In other words, friction is heating the cam which in turn melts the plastic....? Therefore, nothing to do with electrical current.
 
Will do. It's a process getting the battery out, to then get the battery box off to check out behind. Found a mouse nest atop the battery, but nothing behind the battery box, where the ignition switch and voltmeter are. The clamps and posts on the battery had a LOT of crud between them- easy to clean up, but the battery is about 8-9 years old, so I'm going to get a new battery before I proceed. I'm losing sunlight, and no place to get this tractor out of the weather where there is lighting. Neither of my boys are home to help push this to a pole shed just to get it under a roof. I'm licked for now, but I'll let you know how it all works out.

Thanks for the help.
 

Are you lubing the plastic wear block with the correct grease? Installed dry the wear block will not last long.
 
The coil should have about 3 to 4 ohms across the small terminals. If more like 1.5 or less, the coil is bad, and not going to get better. A 6 volt coil should have 1.8 to 2.5 ohms. that would need a ballast resistor if used on a 12v tractor. Since your coil worked for a long time it is the thing I would suspect first. Jim
 
(quoted from post at 16:29:53 11/04/18) Excessive current will heat the points enough to melt the plastic blocks.

I am having trouble with this. When the points are closed the resistance should be zero, therefore no heating. With the points open there is no current, therefore no heating. Where/when does the heat come from....is it the arc as the points break open?

I am not saying you are incorrect...just asking to understand.

Thanks
 
First thing I would do is check the voltage between a good ground & the positive on the coil. Verify that the voltage is where it should be. The second thing would be to try another coil. The resistance in the coil could be about right when cold, but takes a wild swing when hot. Usually they just burn out, but maybe not yet in this case. I think it would be worth try to change. Just my two cents.
 

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