turning off AC before shutting off car?

[Letxen3]

is it true that if you shut down your AC before turning off the car it will help prolong the life of your AC compressor?

Topic

[Dan]

I thought you were going to ask a different question, so I hope you don’t mind that I’m going to add it.

In some cars, probably not the newest models, if one were to leave the HVAC blower setting on anything but the “off” position, with the engine turned off and the key removed, will this cause a key-off drain of the battery?

[Bryan Carter]

[quote=”Letxen3″ post=108417]is it true that if you shut down your AC before turning off the car it will help prolong the life of your AC compressor?[/quote]
I’m sorry, but there are too many variables in compressor design and electronic engine management to provide a simple yes or no answer.

[college man]

[quote=”Letxen3″ post=108417]is it true that if you shut down your AC before turning off the car it will help prolong the life of your AC compressor?[/quote]

I always shut off the AC before the car. My main reason is when I go to
start the vehicle I’m not trying to start against the AC. 🙂

[Bryan Carter]

[quote=”college man” post=108498]
I always shut off the AC before the car. My main reason is when I go to
start the vehicle I’m not trying to start against the AC. :)[/quote]

Funny you should mention that… some automakers employ a strategy of specifically turning on the compressor during cranking. They do it with the intention of extending compressor life. When the engine is off, the high and low side pressures can equalize causing liquid refrigerant to condense in the compressor. Turning the compressor on at relatively low speeds (such as during cranking) can safely drive this slug of liquid out. The technique is known as “anti-slugging”.

My point is that the ECU can (and sometimes does) cycle the compressor on or off regardless of driver input, or what the dash controls are set for. That’s one of the reason I said it was a question that couldn’t easily be answered.

[Bob]

When running my AC I usually shut it off a mile or so before my destination. My reason is that I hope to blow condensate off the evaporator and reduce chance of mildew. May be bogus; but it helps me feel good.

[Author]

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