A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Why don't auto headlights go off when you turn off the ignition?

March 2, 1990

Dear Cecil:

Why don't auto headlights go off when you turn off the ignition? Is it a conspiracy to sell more car batteries? I can't think of a reason the headlights need to be switched independently of the ignition except possibly when you lose your keys at night in front of your car.

Cecil replies:

Time for another adventure in industrial anthropology, which consists of getting the natives to ask themselves, why do we do this, anyway? Being a little vague on headlight theory (I was asleep when they covered this in know-it-all school), I called up the car companies. Results: total double-talk.

The Ford guy pinned it on "cost and complexity" — as though making the headlights go off the same way the windshield wipers do would be a spectacular feat of technology. The GM lady helpfully noted that on pricey models you can get a high-tech option called a "twilight sentinel," which turns the headlights on and off automatically with the engine, depending on how dark it is out. A typically American example of a pile-driver solution for a thumbtack problem, and certainly not an answer to the question.

The GM lady then threw up a smoke screen: you want your emergency blinkers to operate independently of the ignition so you won't have to leave the key in the car when you go for help. No doubt, ma'am, but I wasn't asking about the emergency blinkers. Well, she said, sometimes you want the dome light on without having the key in, don't you? Uh-huh. Obviously we were getting nowhere.

The Ford guy, meanwhile, had come up with what I suspected was the real answer: we've always done it that way, and nobody ever complains. Jeez, I think to myself, don't you guys ever respond to the inner muse? Where is our pride in getting the job done right, regardless of the madding crowd? But you can't expect these guys to understand poetry.

I called up Consumers Union. Surely, I said to myself, these flinty-eyed watchdogs will cut through the BS. Ha. I learned the following: in some foreign makes, the ignition does shut off the lights, and anyway there are times when you want to be able to operate the radio or beep the horn with the ignition off. Cecil, of course, had not asked about the radio or the horn and did not care what foreign manufacturers did.

Finally the GM lady called back. She had been asking around, and the consensus was as follows: (1) it's a security measure — I mean, come on, we can all dream up some off-the-wall scenario in which you'd want to be able to turn the lights on with the ignition off; and (2) customers expect it to be that way, they're not complaining, so why rock the boat? Seems pretty silly, but if so, the fault, dear Curious, is in ourselves, that we sit still for it.

Why the lights don't go out: A Colloquium

Dear Cecil:

By now millions of true geniuses must have let Cecil Adams know the real reason the ignition doesn't turn off the car lights. Because if they turned off automatically they would turn on automatically. Everyone would drive all day with their lights on. Or there would be a turn-off switch for days and we would be back to square one. Or we would pay $50 or $100 for a sensor that would turn them off in daylight. Too simple for you?

Cecil replies:

Perry, my friend, you and Detroit were meant for each other.

Dear Cecil:

I think it's great you can turn the headlights on when the ignition is off. I can think of countless times I used the headlights and wanted the ignition off. As a matter of fact, I had a VW Bug that automatically shut off the lights when you turned off the ignition and it drove me crazy!

It's obvious you are used to living in an area where there are lights on every corner. Didn't you ever have to work at night where there were no outside lights? How about trying to fix a car at night when nobody has a flashlight? It's usually more than a five minute job, and you wouldn't want your car running the whole time.

Didn't you have any fun growing up? We used to park our cars in a field and dance in front of the headlights. On foggy nights we would plan to meet friends at an old graveyard, get there early, TURN OFF THE IGNTION, and wait. When our unsuspecting friends would arrive, WHAM, on went the headlights! It scared them to death! (Sixteen-year-olds in small towns have to find something to do!)

What about arriving at a campsite after dark and trying to set up camp? How much gas would you waste if you kept your car running while you were trying to figure out that "easy three step tent"? You couldn't leave the campsite because you'd be out of gas!

I used to ride my horse at night and car headlights were perfect for lighting up my riding arena. My horse would not have put up with a running car.

There are lots of reasons to have your headlights on when the car is off. You just have to think about it.

Cecil replies:

Keep reading, Einstein.

Dear Cecil:

As a longtime fan I feel I must comment on your recent column about headlights. A couple years back we rented a GM car. When we started to get out with the headlights on, a sensor of some sort activated a buzzer. By contrast, on our Toyota, when I open the door with the headlights on, a sensor activates a shutoff switch. Thus I could never run down my battery by leaving the headlights on. For those rare occasions when I want my headlights on, I need only turn them off and on again; then they stay on. The common sense behind Toyota's approach, at what must be almost exactly the same production cost as GM's, is in my mind one of the major reasons why American car manufacturers are falling behind the Japanese.

Cecil replies:

Agreed, but the buzzer is better than nothing. As of a few years ago I'm told you could buy a little gimmick for about five bucks at auto parts stores that, when installed, would beep if you shut off the ignition before dousing the lights. It's not as effortless as Toyota's approach, but it beats a dead battery.

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