Nawlens Gator
Member
I posted the last 3 days about a recurring hot coil issue on a '72 IH 140. It is 12 V neg ground with 10SI alternator and Pertronix electronic ignition. Tractor runs great for 30 min to one hour then spits, sputters, and cuts off. It won't crank back up. I notice the coil is red hot (and I’ve installed new coils several times included the Pertronix recommended coisl and an ic14SB coil from Napa) when this happens and the ammeter shows a large current drain. I switch the key off and after things cool for around 30 min it cranks up, all seems normal, and things repeat. The alternator was just replaced and the output remains steady at 14.6 V.
Yesterday I installed a 1.6 OHM ceramic encased ballast resistor in the wire from the ignition switch to the + coil terminal per several posters suggestions. This dropped the voltage to the coil from 11.5 V to 8.5 V (measuring from the + coil terminal to the frame). The current must be 3/1.6 = 1.9 amps. I hooked the red wire from the ignition module to the coil input terminal (+) instead of the ballast resistor input terminal as the Pertronix instructions say. Pertronix assumes if a ballast resistor is in place, you probably have a 6 V coil. I use 12 V “no resistor required” coils with resistances anywhere from 3.1 to 3.4 ohms.
Today I mowed for over an hour and had no ignition problems at all. The coil was warm but I could hold my hand on it with no problems (before it could burn you if held for > 3 sec). It looks like a red hot coil somehow causes problems in the Pertronix ignitor ignition module. The Pertronix rep says the hot coil is normal, it’s just coincidental, and the problem is elsewhere. I disagree.