Can I leave the AC on in my car?

My wife and I having this debate. She says if I leave the AC on when I turn the car off, it will eventually ‘burn out’ the AC. She says the same thing about the car’s heater. I don’t get it though. She can’t explain how or why this damages the car, just that it does. Can anyone say for sure whether or not you have to turn the fan to the ‘OFF’ position before you turn your car off?

If the engine isn’t running I don’t see how the A/C could be working since the compressor requires the engine to turn a belt to run it… the fan may still be running… but I don’t think the A/C is running and therefore can’t be damaged. But IANAM (mechanic).

I don’t think she means that the AC is actually ‘ON’ and running, just that I’ve left it in the ‘ON’ position as I turn the car off. Then when I start the car up, the AC starts up again. She says I must turn the AC to the ‘OFF’ position before turning the car off or on. I guess it’s like unplugging a computer without shutting windows down? AFAIK, the AC is not a Microsoft product.

Most cars today shut off any electrical device briefly (radio, A/C, heater) that would prevent you from getting the ignition started.

In my car (a Camry) the radio usually goes off for a second after I start the car up. I will try to notice what’s happening with the A/C.

The AC is belt-driven from the engine. It is not possible to burn it out by leaving it to the “On” position. It does have a magnetic clutch and fan, those are not powered when the car is off either. There is no concern whatsoever.

She is incorrect on both counts. The AC has been discribed already so I won’t go into that.

The “Heater” has nothing to get “burned out”. The heater core is what gets the air “warm”. It is nothing more than a small radiator looking type thing. Your engine coolant flows through it on its way back to the radiator. Your fan blows through it, hence the warm air you feel. Since it is mearly coolant passing through kind of a labryinth there is really nothing to fail… other than it corroding over time but that would happen eventually over a long time anyhow (just as a radiator would).