Shorting through the points

[Model A Apprentice]

Having a difficult time looking for a short in the distributor. The system is has power through to the points arm. Testing for up to 15 minutes with the points open, the ignition system is stable with power to the points arm while the points are open. When the points are closed for several seconds, a thin trail of smoke comes from the contact of the points and the fuse blows. With power off and the points open, checking with an ohmmeter shows the points to be isolated from the upper plate and dist body. With power on and points open, voltmeter shows 6 volts to the points arm.

Any ideas?

What I have done so far:
- disconnected all wiring for the lights/horn through the steering column
- disconnected headlight and horn from the cut out
- tested generator and cutout with ohmmeter for isolation. tested good
- replaced the ignition switch and steel cable
- replaced the upper and lower plates
- replaced the points
- replaced the spring between upper and lower plates
- re-installed the condenser, isolation washer is installed
- reconnected ignition cable so it is just activating power to the dist.
- tested new upper and lower plates for isolation and tested fine
- tested new and old points for isolation and tested fine
- verified that the wire connecting upper and lower plates is isolated
- had a beer and thought about it a lot

[82ndscotty]

sounds as if you have an internal short in the coil decreasing the resistance thus allowing more amps to flow thru to the points. scotty

[Model A Apprentice]

Originally Posted by 82ndscotty

sounds as if you have an internal short in the coil decreasing the resistance thus allowing more amps to flow thru to the points. scotty

You are a GENIUS! Changed the coil and (so far) no blown fuse. Thanks Scotty

[Tom Wesenberg]

Your coil may be good! Make sure you have all the parts for the terminals, first thing to go on is AN INSULATING WASHER, then a flat washer, lock washer, then nut, then the lock washer and nut for the wire terminal. The same parts are used on both terminals. I've seen one or both insulating washers left off, and the person thought the coil was bad.

[82ndscotty]

Tom, if it was grounding at the coil no current would be going to the points.[for your information] scotty

[Tom Wesenberg]

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Originally Posted by 82ndscotty

Tom, if it was grounding at the coil no current would be going to the points.[for your information] scotty

Yep, I thought of that right after I posted it, but forgot to edit it. Thanks

[1931 flamingo]

When i replaced my coil recently, I did NOT notice and insulating washers on old coil and e/thing seems to be fine.
Paul in CT

[Tom Wesenberg]

Originally Posted by 1931 flamingo

When i replaced my coil recently, I did NOT notice and insulating washers on old coil and e/thing seems to be fine.
Paul in CT

If the studs come through bakelite or some other non conductor, then you don't need any insulating washers. On the 28-9 slant pole coils, the studs pass through a metal cover and need the insulating washers.

[1931 flamingo]

Ah so, thanks tom, mine's a 31.