Auto Airconditioning Shut Down Procedures

[ROBERT ESPOSITO]

Hello Again to All.
I just purchased the 2004 Malibu LT. It has the auto Climate Control. My question is this. When it is in the Auto mode and you shut off the engine should you move it to manual before start up, or is it O.K. to leave it in Auto Mode? I never wanted to start a vehicle with the compressor engaged, with manual air, I always shut down the airconditioner before shutting down the engine. Thank You Bob.

[Rhcmlc]

I thought I was paranoid because I always turn off the a/c before shutting down the engine. It's actually a good thing to do because it places less stress on the motor during start-up. I don't know if changing the a/c from auto to manual makes a difference but definitely try to turn it off completely before shut down.

[danv]

I don't really think it makes a difference. On my '04 Malibu LT, I am almost positive that the air conditioner clutch only kicks in after the motor has been running a few seconds. There is an audible click when it engages.

[e2helper]

danv is correct. Just leave it in auto mode.

The engine controller is the final decision maker in regards to when the A/C compressor is on or off. So they will inhibit operation until engine is running.

Believe it or not under some conditions evens if you had the A/C turned off the compressor will be turned on very briefly DURING an engine start to remove the liquid refrigerant that might have collected in a/c lines. The noise that this creates is masked by the engine starting (which is why it is done this way).

The engine controller also will shut down A/C compressor temporarily under all kinds of conditions. Things like wide open throttle (when you are requesting maximum engine power), to help prevent an engine stall (reduce load on engine), etc.

So maybe a long time ago shutting off the A/C compressor made sense prior to engine starting but now the computers in vehicle will handle that for you.

Blower motor doesn't operate when engine cranking either so you don't have to worry about that. Actually on your vehicle the control head for auto airconditioning also ramps up the blower motor speed.