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#4475458 - 07/31/17 11:14 AM Turn A/C off first before shutting off engine?
55Test Offline


Registered: 09/22/04
Posts: 1972
Loc: New Brunswick
I've always wondered, should you shut your AC off first before shutting your car off? I always do whenever I drive someone's car (my AC doesn't work) but I never see anyone else do it. Am I just being nitpicky?
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#4475462 - 07/31/17 11:20 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
bioburner Offline


Registered: 09/19/16
Posts: 1418
Loc: Minnesota
Before power management systems I would turn off before shutdown and even a block or 2 before to prevent odors. Newer vehicles its probably not an issue
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#4475463 - 07/31/17 11:21 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
DBMaster Offline


Registered: 09/18/12
Posts: 5323
Loc: DFW
I am in the habit of doing it, too. But, it's because my dad told me that if I didn't I would be forcing the starter to turn the A/C compressor when I restarted the engine. This was on a 1972 Pontiac so who knows, it may have been true. I don't think it really matters anymore, but old habits like this are really hard to kick.

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#4475464 - 07/31/17 11:21 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Bud Offline


Registered: 06/04/02
Posts: 1721
Loc: Texas
I would say nitpicky.
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#4475466 - 07/31/17 11:22 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Johnny2Bad Offline


Registered: 05/20/13
Posts: 1810
Loc: Saskatchewan, Canada
I normally turn everything off before shutdown, I want a clean start with minimal electrical load and where I can hear the motor and mechanicals before getting underway (to listen for any unusual sounds/noises). A/C would be no different.
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#4475467 - 07/31/17 11:22 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
ARCOgraphite Offline


Registered: 05/17/09
Posts: 11970
Loc: N.H, U.S.A.
You should shut the A/C down a few Miles/Minutes before you plan to shut off the car but leave the interior fan running.
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#4475480 - 07/31/17 11:31 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
69GTX Offline


Registered: 09/23/15
Posts: 3815
Loc: Connecticut
I figure turning the AC off a few minutes before stopping the car gives the water droplets in the engine bay a chance to evaporate quickly. In any case, I don't want the AC running as soon as I start the car next time. For one, depending on your starting rpm in fast idle (1500-2000 rpm+) your AC compressor spins right up from 0 to higher rpm. The only thing worse is turning it on when at highway speeds (2500+ rpm). Surely this is not ideal for compressor longevity. I'd much rather turn on my AC when the car is at low idle (800-1100 rpm). It will then ramp up with engine speed.
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#4475484 - 07/31/17 11:36 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
demarpaint Offline


Registered: 07/03/05
Posts: 29786
Loc: NY
I never gave it much thought. In 40+ years of driving I typically turn AC of heat off just before I shut the engine. I've never had any AC problems, other than Ford's leaking "O" rings, and a pin hole in 20+ year old AC hose.
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#4475489 - 07/31/17 11:49 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 3970
Loc: New England
I will always shut the A/C off before shutting the car down, but usually only a few seconds before.
Don't know why...I leave the heat on when it's cold, never even really thought about shutting that off before shutting the car down unless I expect it to be MUCH warmer the next time I turn the car on.
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#4475496 - 07/31/17 11:53 AM Re: Turn A/C off first before shutting off engine? [Re: 69GTX]
Chris142 Offline


Registered: 06/05/03
Posts: 16832
Loc: Deplorable in apple valley, ca
Originally Posted By: 69GTX
I figure turning the AC off a few minutes before stopping the car gives the water droplets in the engine bay a chance to evaporate quickly. In any case, I don't want the AC running as soon as I start the car next time. For one, depending on your starting rpm in fast idle (1500-2000 rpm+) your AC compressor spins right up from 0 to higher rpm. The only thing worse is turning it on when at highway speeds (2500+ rpm). Surely this is not ideal for compressor longevity. I'd much rather turn on my AC when the car is at low idle (800-1100 rpm). It will then ramp up with engine speed.
the compressor is constantly cycling on and off. even @ highway speeds.
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#4475499 - 07/31/17 11:55 AM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
E150GT Offline


Registered: 03/11/12
Posts: 1106
Loc: San Antonio, TX
I don't do it before shutdown but I do it before starting. Modern cars should delay the compressor kicking on until oil pressure is up I believe.
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#4475509 - 07/31/17 12:06 PM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Nick1994 Offline


Registered: 02/19/13
Posts: 10118
Loc: Phoenix, AZ
My A/C turns off when I turn the car off. Too hot here to drive without A/C before getting home.
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#4475512 - 07/31/17 12:10 PM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Yah-Tah-Hey Offline


Registered: 05/26/14
Posts: 3409
Loc: Columbus,Nebraska
Turn off all electrical load before shutting the engine down.

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#4475514 - 07/31/17 12:11 PM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
Alfred_B Offline


Registered: 05/12/15
Posts: 1968
Loc: America
In my car the AC is always on, even during winter. The climate control uses it for moisture control. Not much point in fiddling with the buttons -- set the temperature and the car decides the level of AC and/or heat. The car has a huge battery in the trunk so that's not an issue.

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#4475519 - 07/31/17 12:23 PM Re: Turn A/C off first before shutting off engine? [Re: 55Test]
mightymousetech Offline


Registered: 04/03/17
Posts: 1444
Loc: Ontario, Canada
I always turn off my A/C several minutes before shutting the car off. I hate the smell when the evap is left damp and bacteria grows in there.
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