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Does AC compressor cycle in defrost when cold outside?

This is a discussion on Does AC compressor cycle in defrost when cold outside? within the Technical / Maintenance forums, part of the General Discussion category; Does the AC compressor cycle when I have my defrost on? I couldn't get it to come on today even ...

  1. #1
    Because I Said So... srlbotanical's Avatar
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    Does AC compressor cycle in defrost when cold outside?


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    Does the AC compressor cycle when I have my defrost on? I couldn't get it to come on today even with the AC on. Its cold as heck right now, does the compressor cycle when temps are real low?


    • 97 Chevy 4x4 extended cab 5.7L, the Daily Driver
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    Re: Does AC compressor cycle in defrost when cold outside?

    I know mine does but we consider 40 to be cold here in houston,tx

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    Resident Dick Quyonmob's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    Mine does.

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    2000 Chev Silverado 5.3L excoelis's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    Mine doesn't and it is -20 degrees here

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    Because I Said So... srlbotanical's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    Well, i am hoping it works again when it gets warmer...

    I have a feeling its toast.

    • 97 Chevy 4x4 extended cab 5.7L, the Daily Driver
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    The Bad Guy Gran Patron's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    I think it's so suppose to cycle at all times when it's on the defrost mode. Everytime I put mine on defrost,no matter the temp outside, it has turned on.


    Funny cause I had a lady come is the service drive and ask why the compressor kept coming on when on the defrsot mode. I told her it was suppose to do that.

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    Re: Does AC compressor cycle in defrost when cold outside?

    I think when it's low on oil, it cycles on and off. Thats what I was told.

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    Because I Said So... srlbotanical's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    I did a little checking around and the compressor should cycle in defrost. No doubt about it.

    My next step is to see if I am low on coolent oil, and all the electrical conectors are in place...

    • 97 Chevy 4x4 extended cab 5.7L, the Daily Driver
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    You spent what on tools?!
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    Re: Does AC compressor cycle in defrost when cold outside?

    its supposed to cycle on, the way gm does it is they bring in the moist ouside air, run it thru the ac system to dry it, and then super heat the dry a/c air to defrost your windshield. i litteraly learned about that on friday. it doesnt make sense, but then again... it does lol.

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    Re: Does AC compressor cycle in defrost when cold outside?

    Every car on the road made in the last 6 years or so that has an air conditioner works this way. The idea is to dry the air so as to not cause condensation.

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    maliburacing freak J-Rod's 85sb's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    Quote Originally Posted by tdoyle
    Every car on the road made in the last 6 years or so that has an air conditioner works this way. The idea is to dry the air so as to not cause condensation.
    Quote Originally Posted by campaug86
    its supposed to cycle on, the way gm does it is they bring in the moist ouside air, run it thru the ac system to dry it, and then super heat the dry a/c air to defrost your windshield. i litteraly learned about that on friday. it doesnt make sense, but then again... it does lol.
    X2 it aint broke dont fix it. wait till it gets warm to see if it stays on. it will cycle also on cooler days 60s-70s should stay running the hotter it gets. the only real way to check is to see what the pressures are. mine will cycle on a 90deg day but will blow 40 deg out the vent it all depends
    Last edited by J-Rod's 85sb; 02-12-2007 at 12:46 PM.

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    Re: Does AC compressor cycle in defrost when cold outside?

    You probably need the ac system serviced. there's a safety switch that keeps the compressor clutch from engaugeing when the system is low on freon.

    Don't wait get it serviced.

    This is a safety item. Not just a summer comfort thing. It does make a big differance in defroster performance.

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    Gold Member Sierra Stud's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    I remember reading somewhere that the a/c won't kick on below a certian temp... i.e. 40*f. I think I read it on here somewhere or in my '06 GMC manual.

    2006 GMC 1500 Z-71, RC Leveling kit, 285's, Line-x'd bumpers.

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    Because I Said So... srlbotanical's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    Just a quick update. I did a pressure test and it was fine. I also picked up a can of NAPA recharge coolant/oil and it took the whole can. So, I either have a leak and the system was totally empty, or I need a new compressor... Me thinks.

    Steve

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    Knuckle Buster Coefficient's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    When the compressor goes bad they make lots of noise. With your motor off try turning it with your fingers. You should be able to grab the clutch in front of the pulley and give it a turn. If it turns your good, if it don't... well. If your system has a leak, that oil will be all over the fittings or even the compressor.
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    Re: Does AC compressor cycle in defrost when cold outside?

    Quote Originally Posted by Sierra Stud
    I remember reading somewhere that the a/c won't kick on below a certian temp... i.e. 40*f. I think I read it on here somewhere or in my '06 GMC manual.
    Correct - you don't want the darn compressor running when it's super cold outside.

    The pressure switch went out on my Blazer, started up with defrost on @ 5 degrees F, blew the compressor to pieces due to thickened oil in the system.

    When it's cold, I always turn the A/C off before starting just to be safe.
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  17. #17
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    Re: Does AC compressor cycle in defrost when cold outside?

    If the pressure checked out ok you can rule out a leak.The system will still take and extra pound.
    Sounds like the LOW PRESSURE SWITCH is acting up. It's located on the acumulator, thats the big silver tank on the pass firewall. Give the switch a few light taps, if it starts running
    the switch is bad. To check the whole elec system jump the connector with a paper clip. If it runs the the entire elec system is eliminated. The prob lies with either a bad switch or low sys press. Since the pressure is ok looks like the switch.
    Pressures should be around 40-60 psi low side and around 150-200 psi high side. Pay no mind to the low side watch the high. If below 100psi system is low........hope this helps

  18. #18
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    Re: Does AC compressor cycle in defrost when cold outside?

    On my Ford it said right in the owners manual that below 30 deg the compressor will not run when set to defrost. Cold air is dry air. It doesn't need dehumidification. Thats why people put humidifiers on their house heating systems. Cars without AC (If you can still find one) defrost just fine in the winter. Now I don't know about my Chevy, but there really isn't any need for it to run when it's below a certain temp.

  19. #19
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    Re: Does AC compressor cycle in defrost when cold outside?

    yea right come to houston where cold air is humid air.lol

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    Dont Worry, i'm a pro ;) gmcman7202's Avatar
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    Re: Does AC compressor cycle in defrost when cold outside?

    ya but to you cold air is warm air to me....

 

 
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