It was pointed out to me a while ago that copper has a pretty serious
temperature coefficient of resistance - 0.3 percent per degree C. What
that means is that if the starter gets baked to 100 degrees C (the
boiling point of water) it would have 30 percent more internal
resistance compared to being at 0 C. This doesn't reduce the power
output by 30 percent but it does reduce the stall torque limit by about
that much. On the other hand, it would be quite possible for a motor to
heat-soak to a significantly higher temperature, with consequently
greater resistive loss. The copper wiring in the engine compartment is
similarly affected, so if you start with a poor connection and add to it
a bunch of copper loss, you can go to a no-start or even a no-crank
condition.
Theo
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