My wife has developed a habit that I think may be detrimental to the family vehicles. When she parks the car, she sets the auto transmission to park and turns off the key. She does not turn off the air conditioner or even the radio. Therfore, when the next person to use the vehicles hops in to start it, he’s hit in the face with hot air and perhaps some music.
Now, I’ve always thought it a good habit to turn these things off. It seems like it would be easier on the engine and the components to start one at a time. I also think it’s simply a good routine when parking a vehicle. When I park the car, my hands follow a set routine – park, brake, air, radio, lights, wipers, seatbelt, door. My hands even touch the lights and the wipers even if they’re not on. It has simply become a habit.
So, when my wife says, “How is this bad for the car?” what do I tell her? Or, do I just figure that a few repair bills are worth my wife’s vehicular happiness?
While your practice of turning everything off is probably marginally better for the car, the overwhelming majority of drivers leave everything on like your wife does.
I don’t think there’s a convincing enough argument here to make your wife change her ways. If this is the biggest thing she does that bothers you, count yourself lucky!
I was always taught to turn of the A/C before shutting off the engine. The rationale I was given by my Dad was that the compressor represents an additional load on the battery/starter that should be minimized wherever possible, especially if you have minimal battery power.
The only thing that could be a problem for the car is trying to use the battery to start while all those accessories are placing additional load on the electrical system. However, I believe that most cars nowadays disconnect the accessories when the key is moved to the start position to avoid this very issue. Once the car is running, I don’t think it causes damage to turn on multiple accessories at the same time. I don’t think there’s anything about suddenly adding a large load that could damage the car, even over time, when the car is designed to carry that load.
Now try plugging an air pump and a TV/VCR into your cigarette lighter at the same time, who knows.
How many times have you heard someone say “My <widget> just failed, and the mechanic said it was because I didn’t turn it off before I shut the car off!”?
Answer? Never.
It may be slightly harder on the battery/alternator/starter whatever to have to start all these devices at once (assuming the manufacturer hasn’t designed some kind of protection against this already), but I think it’s safe to assume that more major things will fail on your car before this ever becomes an issue (like the engine, transmission, floor panels, etc.)
The biggest consideration would be whether the car is a well-maintained, good example of its species, or whether it’s a piece of junk just waiting for an opportunity to fail.
As for A/C, if you live someplace really hot (like I do now), you should make sure that the A/C isn’t left in recirc mode or off, i.e., make sure there’s a vent to the outside world.
It is harder for your engine if you start the car with the A/C on. That’s why your car will automatically turn the A/C off while it starts the car. The car will also automatically turn the radio and most other “accessory” devices off while starting.
Since your car is smart enough to handle it, you don’t need to be worried if you leave the A/C or the radio on.
i’s not a load problem - it’s a mold problem. Shutting it off with the evaporator wet can lead to mold and mildew growth in the evaporator case and some really foul smells. If you remember to, turn off the AC about a minute before shutting off the car and/or blower - just turn the control to “vent”
Accessories like the A/C compressor, blower, wipers, radio, turn signals and such are not energized when the key is in the “start” position and likely never were on any car.
Slightly, and here’s why. If you turn off your AC for a bit before stopping the car, it will prevent that weird 'musty" smell which is caused by mold growing in the AC, due to the dampness. So, yes, you should turn it off (but leave the fan on), and do it about 5 minutes before turning off the engine.
I’ve heard the same thing as Dr Deth and gotpasswords, that you should turn off the AC and run the regular vent air through for a few minutes to avoid horrible mold, mildew, etc. I wonder if Cartalk has addressed this?
Everyone who lives in FL turns their A/C when they leave the showroom and don’t turn it off until the car dies. Your car will be fine. My family (who mostly lives in FL) have never had a problem with mold. I run the A/C nearly all the time in the winter up here for the defroster, never shut it off, and have never had a mold problem.
The one thing that does remain on while the key is in the start position is the lights. The lights are the only thing you should shut off while starting the engine.
But why? It won’t hurt your car, unless your battery is almost dead. But then you shouldn’t have the lights on without the alternator running anyway.
The definitive answer is this: leave whatever you want in any on/off position that you want when you start or turn off your car. Any difference in load or wear is so miniscule that if you need to worry about it, then you just can’t plain afford to drive and you should go buy yourself a good, second-hand skateboard and some good shoes.
Consider this: I’ve got automatic headlights. I don’t have to every touch them. They come on and off as needed. Climate control, too. It’s set, and I never touch regardless of what the season is. Do you think the manufacturer intended for me to have to worry about stupid crap like that for starting the car?
Mold? Can’t say – never been a problem in Michigan for me, although I’ve heard of it being problems for people. Because of the climate control system and its total hands off approach, I guess that’s up to your individual circumstances. But it’s not related to the car.
Thanks everyone for the wonderful replies. I will now procede to obsess on some other of my wife’s annoying habits.
Just kidding, she’s really great. This was just bugging me. I’m glad to get this off my chest and now I don’t need to worry with it.
The car’s owners manual says that it won’t start the air compressor until thirty seconds after engine start, regardless of what the dashboard switch says. The recirculate switch is electronic and resets to outside air every time the a/c is turned off. I don’t think that dampness is going to be a problem and both a/c’s (it’s a van w/ rear air) drain very well.