Shouldn't the primary circuit be open with the key in the OFF position?

[Baltimore Sailor]

This past weekend I was out with the kids and had a heat-related shutdown. (What I mean is that it overheated and I shut it off.) But the strange thing happened later after the engine cooled off.

I restarted it with no problem, but when I turned the key off to stop it, it kept running. It finally died on its own when I put it in gear at low throttle and it stalled.

Later I put a multimeter on it, and found that there was continuity between the positive terminal on the coil and the output terminal on the alternator even with the key in the OFF position and the battery switch OFF as well.

Is that right? I thought that the primary circuit was open until the key was turned to the START position to allow current to flow to the starter and the coil to start the engine, and then when the key was released it went to the ACC position to allow current to flow from the alternator to the key to the battery. Is the circuit different than I'm thinking? Is there a reason that there should be a circuit from the alternator to the key to the coil even with the ignition in the OFF position?

Thanks!

[Don Moyer]

I think this is the indication you'd get if the diode is shorted in the field flashing lead between the alternator and the positive terminal of the coil. I'd remove the field flashing lead from the coil and see if the continuity between the output of the alternator and the coil disappears.

Don

[Baltimore Sailor]

If the continuity does disappear, what do I do then? Is this an indication of a failure of the alternator? But it appears to be charging just fine when the engine is running.

When I ran the engine most recently to test the thermostat, the engine shut down just fine with the key. Could that have been heat-related as well?

[Don Moyer]

I'd take the alternator in to a local automotive starter/alternator repair shop to be checked out. I don't believe your alternator problems are heat related.

Don