Car Talk Should accessories be turned off when shutting off the car?

DEAR CAR TALK:

When I was learning how to drive back in the 1970s, I was told that before turning off the car, a driver should first make sure all of the accessories (wipers, radio, heater blower, rear window defroster, etc.) are turned off.

The idea was that it would be “easier” and better for the car to not have to power everything all at the same time when you next start the car. Also, if you have a weak battery, better to have it using all its juice to start the engine only, instead of all the other stuff, too.

Was that true back then? If so, is it true now?

– David A: It was true generations ago, David, but it’s certainly not true now. On modern cars, all of the battery’s power is automatically directed to the starter motor when you turn the key to the crank position. Anything else that draws power is automatically shut off while the car is cranking. The car takes care of that itself. You don’t have to do it.

You can demonstrate this for yourself, David. Next time you go out to start your car, before you start it, turn the key to the “run” position (right before “crank”). Then turn on your windshield wipers.

They’ll start wiping. If you then turn the key to the “crank” position to start the engine, the wipers will momentarily stop while the car cranks, and then start moving again once the engine is running. And that’s true for every accessory.

In the really old days, you may remember that if you’re lights were on, they would dim when you cranked the engine -- as the starter motor drew most of the available electric power.

So back then, it made sense to be sure to turn your lights off when you turned off the engine the night before. Of course, it made sense to turn your lights off the night before anyway, because if you didn’t, your battery would be stone-cold dead the next morning.

In any case, it makes absolutely no sense now to worry about turning off accessories when you turn off the engine. The car has that covered. The only exception is that, if you live in the great, frozen north, you should turn off your windshield wipers when you park your car outside in the winter.

That way, if you get heavy snow or freezing rain before you come back to start your car, you won’t strip your wiper transmission when the wiper arms flash-freeze to the windshield and then try to start wiping the second the car starts.