Michael,

The resistance of copper wire increases with temperature. It seems strange that the secondary resistance with your original coil did not increase with a 105 degree increase in temperature. According to one website I looked at, a 100 degree rise in temperature should cause the 8000 ohms to rise to 9600.

I believe that when a coil doesn't work properly when it is hot it is because the insulation in the secondary has started to fail, and the electricity does not go through the whole winding, but jumps between some of the turns. This however seems opposite to the NOS coil, where the resistance is high (no short circuits between turns) with increasing temperature, yet it became weak when hot!

I once had a coil which got weaker and weaker as it warmed up. I had to press less and less on the gas, until it would only Idle and finally the engine stopped. This was my fault, because I had one spark plug wire removed because a connecting rod was loose, and I made the mistake of not grounding it. Therefore the voltage had nowhere to go, and broke down the insulation in the coil.

I have more often had coils fail suddenly (with no spark, or with a weak spark like you had with the hot old coil).

Per

[quote="Michael Cohen" post=13446] I didn't try it (yet) with the NOS one I recently purchased.

Michael,

Do you mean you purchased a NOS AutoLite coil or a NORS replacement coil? If it's NORS, what brand and part #?

Thanks, Per, for the information. I wondered about the lack of change in the resistance on the old coil that I had/have in may car. In that regard, the NOS coil (that exhibited the increase in resistance in the secondary from 7000 to 8000 to 12,000 with increasing temp) would have seemed to behave normally; unfortunately this coil was the one that gave the most trouble. Go figure.

Back to Eddie on his question - the experiments i posted earlier were with my original coil and an NOS Auto-Lite CR-6012A that I bought over the internet. I ordered a new coil from NAPA, ECH IC7, which i will pick up this afternoon and install and test drive over the weekend.

OK folks, so here's the result of the new NAPA coil, part number Echlin IC7. I took the car for a similar ride as last week with no mishaps. I know that doesn't prove anything, but at least it's a step in the right direction. I have amended my table of data with the test results from the new coil added, as well as the specifications from the manual, where available (see attachment).