Chrysler 440 ballast, coil and voltage

Have been working on a 1975 Century Arabian with a Chrysler m440. Dropped the engine back in the boat after redoing the stringers and am working on reconnecting everything. Plugged in the wire harness and went under the dash for a while to test gauges and such with the key in the on position. After about 10 minutes went back to the harness to trace a wire and he ballast/resistor was really hot and the coil was warm. Voltage on the gauge reads 11 volts and if I remove the ignition wire it jumps up to 12.5.

Understanding the purpose of the ballast is to resist current to the coil - but should the voltage read that low while the key is in the "on" position. Thanks.

Start and run circuit voltage is volt tested with the ballast disconnected I do believe. Sounds like your coil was drawing the load on the battery.

I learned the hard way that those ballasts develop almost invisible cracks from heating and cooling. The effect is normal starting when the engine and ballast is cool; but, low voltage and won't crank when the engine is hot. I carry a spare ballast on board now.... which reminds me I need to remember to look to see where I stowed it.

Thanks for the replies. Next question - if the key is left in the on position will it damage the coil? Also will this drain the battery?

.." if the key is left in the on position will it damage the coil? Also will this drain the battery? "

Yes, and yes.

Jeff