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Do modern cars disable unneeded drains on the battery (AC, radio..) while the car is starting?

I have been told that leaving devices on such as the AC, defogger, radio, while starting a car will burden the battery and shorten its life. In my experience this appears to be the case, at least for some cars, as routinely turning off the AC before starting the car seems to have cut down on the need for new batteries and alternators.

So I am wondering if new cars electronically disable unneeded drains on the battery while starting?

The ignition switch only provides power to certain areas when it the START position. It allows maximum power to the starter and also keeps power spikes from the starter getting to things.

In every car I’ve owned, everything shuts down when the starter is cranking, and the A/C clutch doesn’t engage until the engine is running.

In a word: Yes.

Yes, in most cases. I have had cars that don’t turn off the headlights while cranking, but, the added load, if any, is small compared to the starting load, I very much doubt there would be any effect on battery or alternator life.

Yes, modern cars and not so modern. They have been that way for a generation or 2.