Mag Coil problem

Tue Feb 17, 2004 8:33 pm

Maybe one of you fellas has an answer for a friend of mine cause I don't. His dad has a 49 Cub with a mag. He has been experiencing problems with it burning up mag coils of late. Original lasted for 50 years but he has replaced it 3 times since and now needs to again. At first we thought we just "got a bad one" but not 3 in a row! All have been IH parts (mainly cause we haven't been able to find anything aftermarket) one of which only lasted for 32 days (no the dealer would not warranty it). Each time the coil was replaced, so were the condenser and points. Running solid core wires and new plugs also. Only thing I can think of is the magnets in the mag itself may be weak. Never gets worked particularly hard anymore (dad's 87 and mostly just putts around the 40 acres) but never the less is one of those things ya just have to find a proper fix for.
Anyone have any ideas?

Tue Feb 17, 2004 8:46 pm

Take a good look at the core and see if there are any sharp edges or protrusions that could wear through the coil insulation. Make sure the laminations are still lined up square.

Tue Feb 17, 2004 9:02 pm

Another tip: NEVER allow the mag to be turned without a place for the spark to go. When the impulse snaps, a spark WILL be produced, and the spark will take the easiest path. If there is no plug wire, etc hooked up, the easiest path may be through the internal insulation, breaking it down. Some other mags have a safety gap to prevent this, but the J-4 does not.

Tue Feb 17, 2004 11:37 pm

Chuck, Make sure the internal sire from the points to the mag coil isn't rubbing through the insulation and grounding if he is just wanting to keep it running, rather than keeping it original, it is easy to convert it to a battery ignition coil. Remove the internal wire from the points to the mag coil, and the lead from the mag going to the kill switch. Find a place to mount the coil, and run a lead from the + (assuming still positive ground) post of the coil, to the bolt where the kill switch was connected on the mag. Connect the negative - lead of the coil through an on/off switch, to a battery lead. Connect high voltage lead from new coil to distributor cap.

Wed Feb 18, 2004 10:06 am

make sure the kill switch wire to the mag isn't picking up voltage from somewhere

Wed Feb 18, 2004 7:29 pm

Thanks fella's. We'll be doing some checking on it this weekend and just may try running an external coil to see what results we get. If we find anything noteworthy I will let ya all know. Thanks again, Chuck