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Turn A/C off first before shutting off engine? #4475458
07/31/17 10:14 AM
07/31/17 10:14 AM
Joined: Sep 2004
Posts: 1,974
New Brunswick
55Test Offline OP
55Test  Offline OP
Joined: Sep 2004
Posts: 1,974
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?


The total sum of everything I have learned from this website: ...Oil in engine, good!
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475462
07/31/17 10:20 AM
07/31/17 10:20 AM
Joined: Sep 2016
Posts: 1,418
Minnesota
bioburner Offline
bioburner  Offline
Joined: Sep 2016
Posts: 1,418
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



97 Ford E350 D,99 F350 dually D
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Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475463
07/31/17 10:21 AM
07/31/17 10:21 AM
Joined: Sep 2012
Posts: 5,461
DFW
DBMaster Offline
DBMaster  Offline
Joined: Sep 2012
Posts: 5,461
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.

Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475464
07/31/17 10:21 AM
07/31/17 10:21 AM
Joined: Jun 2002
Posts: 1,942
Texas
Bud Offline
Bud  Offline
Joined: Jun 2002
Posts: 1,942
Texas
I would say nitpicky.


2016 Honda Pilot EX-L with NAVI.....Mobil 1 0w20 AFE and Honda OEM Filter
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475466
07/31/17 10:22 AM
07/31/17 10:22 AM
Joined: May 2013
Posts: 2,160
Saskatchewan, Canada
Johnny2Bad Offline
Johnny2Bad  Offline
Joined: May 2013
Posts: 2,160
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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Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475467
07/31/17 10:22 AM
07/31/17 10:22 AM
Joined: May 2009
Posts: 12,283
N.H, U.S.A.
ARCOgraphite Offline
ARCOgraphite  Offline
Joined: May 2009
Posts: 12,283
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.


2014 Nissan Rogue S CVT, OC#10 47272mi-QSUD10W30+5w20 Toughguard Filter; '17 Subaru Crosstrek CVT OC#2 ?? mi-SOA/Idemitsu 0w20 + SOA Filter
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475480
07/31/17 10:31 AM
07/31/17 10:31 AM
Joined: Sep 2015
Posts: 3,941
Connecticut
69GTX Offline
69GTX  Offline
Joined: Sep 2015
Posts: 3,941
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.


----------------

2001 Lincoln Cont 4.6L DOHC/ 39K mi / QS HM 5w30 / FUG XG2
1999 Camaro SS M6 /19K /Mobil 1 0w40 /Fram UG /GM MTL-ATF
1969 Ply GTX/RRs
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475484
07/31/17 10:36 AM
07/31/17 10:36 AM
Joined: Jul 2005
Posts: 30,984
NY
demarpaint Offline
demarpaint  Offline
Joined: Jul 2005
Posts: 30,984
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.


God Bless Our Troops

Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475489
07/31/17 10:49 AM
07/31/17 10:49 AM
Joined: Jun 2015
Posts: 4,436
New England
Virtus_Probi Offline
Virtus_Probi  Offline
Joined: Jun 2015
Posts: 4,436
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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Re: Turn A/C off first before shutting off engine? [Re: 69GTX] #4475496
07/31/17 10:53 AM
07/31/17 10:53 AM
Joined: Jun 2003
Posts: 17,822
Deplorable in apple valley, ca
Chris142 Online content
Chris142  Online Content
Joined: Jun 2003
Posts: 17,822
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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Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475499
07/31/17 10:55 AM
07/31/17 10:55 AM
Joined: Mar 2012
Posts: 1,370
San Antonio, TX
E150GT Online content
E150GT  Online Content
Joined: Mar 2012
Posts: 1,370
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.


1984 Mercedes-Benz 300SD - 100k
1995 F150 XL 4.9 reg cab 5MT - 251k 5w30
2016 Mazda6 Touring 6MT - 57k 10w30
2006 Buick Lucerne CXL 3.8 31k 5w30
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475509
07/31/17 11:06 AM
07/31/17 11:06 AM
Joined: Feb 2013
Posts: 11,090
Phoenix, AZ
Nick1994 Offline
Nick1994  Offline
Joined: Feb 2013
Posts: 11,090
Phoenix, AZ
My A/C turns off when I turn the car off. Too hot here to drive without A/C before getting home.


2015 Hyundai Sonata 2.4L 88k Motorcraft Synthetic Blend 5w30 & OEM
2000 Toyota Camry 2.2L 231k Valvoline 5w30 & Fram Ultra
1996 Jeep Cherokee 4.0L 147k Mobil 1 HM 10w40 & Fram Ultra
Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475512
07/31/17 11:10 AM
07/31/17 11:10 AM
Joined: May 2014
Posts: 3,835
Columbus,Nebraska
Yah-Tah-Hey Offline
Yah-Tah-Hey  Offline
Joined: May 2014
Posts: 3,835
Columbus,Nebraska
Turn off all electrical load before shutting the engine down.

Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475514
07/31/17 11:11 AM
07/31/17 11:11 AM
Joined: May 2015
Posts: 2,011
America
Alfred_B Offline
Alfred_B  Offline
Joined: May 2015
Posts: 2,011
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.

Re: Turn A/C off first before shutting off engine? [Re: 55Test] #4475519
07/31/17 11:23 AM
07/31/17 11:23 AM
Joined: Apr 2017
Posts: 1,481
Ontario, Canada
mightymousetech Offline
mightymousetech  Offline
Joined: Apr 2017
Posts: 1,481
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.


Mighty Mouse Tech
BMW Tech, Former Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
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