Farmall M burns POINTS!!!!

Anonymous-0 · Sep 16, 2009

i have a 1943 Farmall M and it runs good for just a little while after installing a new set of points then maybee after 5 mins the points start to burn and it starts to run roung.. sand the points down and it will run good for awile again. It was 6V converted to 12 and it does have a resitor iline to to wire to the coil. I checked voltage going to coil with tractor off and it was 11V and about 12V when running.. What should the voltage be going to the coil when tractor is running? or is there anything else that could lead to this problem. Thanks

Hugh MacKay · Sep 16, 2009

Trade it for a diesel Deere.

Anonymous-0 · Sep 16, 2009

Have you checked the polarity @ the coil? remember!! the originqal setup was + GND AND THE 12 VOLT SETUP WOULD POSSIBLY BE - GND. CC

dlplost · Sep 16, 2009

check the current thru the points (points closed). anything more then about 3.5 amps will burn them up. resistor may be shorted or the wrong one.

Bob M · Sep 16, 2009

Sounds like the wrong resistor is installed and is sending too much current to the points/coil.

With the ignition "on" and the engine STOPPED you should be see right around to 6 volts across the coil primary. Your reading of 11 - 12 volts is WAY too high.

Suggest installing a new ballast resistor. Get one for any 60's - 80's era Chrysler product - about $10).

Also suggest you spend a couple bucks extra and replace the condenser in the distributor. A failing condenser also shortens point life - though not to the extent you're seeing.

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Or do as Hugh suggests and get a diesel(!)

old · Sep 16, 2009

Bad condenser will cause that problem and that is what the condenser is in the system for to buffer the points to keep them from burning

charles todd · Sep 16, 2009

Definatly sounds like too much current, or gap causing arcing... A red diesel is good to.

CT

John T · Sep 16, 2009

If the Ballast Resistor is sized correctly to match the coil, Id expect more like 5 to 7 volts on the coils input WHEN POINTS ARE CLOSED. If youre putting 11 volts on a 6 volt coil the intended points n coil current is nearly doubled and the coil runs hot plus the points burn up prematurely. Also if the condensor is weak or open the points burn up much sooner but your problem sounds like not enough ballast resistance.

Typical ballast resistors for 12 volt systens rrunning 6 volt coils are in the 1.5 to 2 ohms range, you may wanna check yours.. Or else get a full true (some call internally ballasted) 12 votl coil no ballast required.

John T

scot in pa · Sep 16, 2009

I got Chrysler-replacement resistor on my SM. They have a nice hole in them. I drilled a couple holes in a small peice of metal and mounted it to the coil clamp bolt.

Chrysler also had a wire that ran from the keyswitch to the coil. When you cranked the motor it by-passed the resistor and put 12V to the coil. But as fast as these crank with 12v to the starter, I don't suppose that would be needed too badly.

If you have an old Mopar that only fires when cranking, check the resistor.

TomH in PA · Sep 16, 2009

And don't assume the condenser is good just because it's new. They're made cheap overseas.

Bob Kerr · Sep 17, 2009

Most point type ignitions on 12v ran the coil at 8 volts.

Farmall M burns POINTS!!!!

Anonymous-0

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Hugh MacKay

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Anonymous-0

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dlplost

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Bob M

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old

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charles todd

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John T

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scot in pa

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TomH in PA

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Bob Kerr

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