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Points getting hot

ster1

ster1

Member
Location
Denver, CO
Hi folks. Question for you. I have a Allis Chalmers D15 series 1 that Im having trouble with, but this issue could apply to almost any tractor, so Im posting it here. Anyway, my point is, my points. Theyre getting hot when closed and the ignition is on. Hot enough to start smoking, if I leave it on for just a few minutes. I replaced the coil with a generic one from Napa and added a ballast resistor in series. They still get too hot. Ive never seen this before. Has this happened to anyone else?
 
Yes, they will get hot sitting closed and not running, so will the coil. I've seen coils get so hot they explode!

No reason to leave the ignition on not running. The only thing that saves points and coils from burning up is an engine will almost always stop with the points open.

Todays points are not the quality they once were. The alloys used for making good contact surfaces are expensive, so all the point manufacturer's have miniaturized and substituted cheaper alloys. They are minimally made from the start.
 
Points closed is basically a direct short to ground. Why would you knowingly leave the ignition on with the engine stopped? If you have to have the ignition on for troubleshooting something, turn the engine to open the points, or manually open them and put something for an insulator (like 3 or 4 thicknesses of paper) between them, or unhook the primary wire from the coil. Ignition on and points closed will shorten the already poor life span of the points and may destroy the coil as well, as Steve posted.
 
Measure the current when points are closed, should be 4 or less amps.. Burnt points will also get hot too. Any bad electrical connections will get hot also,
 
Some thing similar happened to me a long time ago on a Ford tractor. Ended up being a bad generator voltage regulator.

Edward
 
The time the points are closed during operation is called dwell. The dwell is near 50% of the rotation total degrees. This means the coil is on 1/2 the time, and off 1/2 the time. This reduces total effective heat to 1/2 of that if turned on not running. I usually don't have disagreement with Steve @ Advance, but in my experience points are almost always closed when engines are shut off. this is due to the compression strokes causing them the stop part way up the compression cycle. Jim
 
Ster, you state Theyre getting hot when closed and the ignition is on.

THATS TO BE EXPECTED I agree with Professor Jim on this one

A tractor almost ALWAYS stops with points in the CLOSED position BECAUSE they ONLY OPEN when a piston is at TDC as that's when they open to fire the spark and since its up on compression it will either roll over or kick back NOT STOP AT TDC with points open.....

With the ignition ON and points typically closed when the engine is setting that's a 100% duty cycle constant current NOT the opening and closing like when running SO THEY GET HOT

John T The view outside my RV window
cvphoto107243.jpg
 
They shouldn't be hot unless they are not making good contact. If they are pitted change the points and set the gap to 19 thousands.
 
Thank you! This was what the issue turned out to be. Put a new set of points in, and yes they get warm, but not hot. Much appreciated!
 

Just curious, why are you leaving the ignition on without the engine running? Great, the new points have better contact and don't get as hot, for now. Current is still passing through, heating the coil and the points unnecessarily, in my thoughts.
 
There are a myriad of reasons someone might leave the key
on. Suggesting otherwise is simply obtuse. Doing such should
lead to a dead battery, not a fire hazard.
 
(quoted from post at 10:32:02 11/08/21) There are a myriad of reasons someone might leave the key
on. Suggesting otherwise is simply obtuse. Doing such should
lead to a dead battery, not a fire hazard.
Click to expand...

What would some of those reasons be?

Trouble shooting the primary ignition circuit is the only one I can think of.
 
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