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  1. #1
    Jr. Engineer vicar75855's Avatar
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    Default A/C 1999 k1500 Suburban Acting the Fool...

    Hey all, I have a '99 k1500 Suburban that has dual air. The a/c in the rear will freeze you out the front a/c just blows lukewarm air most of the time. Since the system shares a common compressor and the rear A/c is working great I don't think it is low on gas what do ya'll think? Has anyone had this prob before? I had a 90 ford van that the blend door broke and it acted similar but I have no idea where that is on the Sub. The chilton book I have here is useless aswell, just referes me to a mechanic....

    Thanks in advance for any help , & all replies.

  2. #2
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    You also have an underhood servo that is vaccum operated (right under your air box) if the vaccum line comes off of breaks that will allow hot air as well. The blend door is in the passenger foot well.. In the entire HVAC unit...
    Mike

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  3. #3
    Jr. Engineer vicar75855's Avatar
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    Thanks for the info I am going to go check the vacum line now hopefully its just a busted vac line I could use an easy fix for once

    Yeah the wife and kids ride in the back where its nice and cold. Ol' dad rides in front in the heat. Now I know what a jar o' sun tea feels like.
    Last edited by vicar75855; 06-05-2010 at 03:16 PM.

  4. #4
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    Have you taken a look at the mixing door servo.. It is on top of the heater/AC box.... i know they can get jammed a little open.
    Mike

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    1997 Chevy S-10 Blazer 4X4 with 330K miles and counting (Hunting rig).

    2009 Saturn Aura XE (wifes car)

    2011 F-150 Crew 4X4

    "Hold it to the floor till you see God.... Then Brake!!!!"

  5. #5
    Jr. Engineer vicar75855's Avatar
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    Ok I am totally dumbfounded.... The back blows great right. Well after checking vac lines and other odds & ends I thought what the heck and added a can of 134a..... the front got cooler. How can the back blow cold on a common comp and the front need gas??? Is there something I am missing here? I added a second can of gas back still blowing cold front got cooler once again. If I wasn't seeing this I would never believe it.

    I am gonna grab some more 134 from town and add another can or so. Thanks for all the replies guys, try adding a bit of gas to yours it might make it work...

    Goodbye all from the Twighlight Zone....

  6. #6
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    What is the pressure??? if you over pressure the system you will blow the compressor up... Do not go over 45PSI.....
    Mike

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    2009 Saturn Aura XE (wifes car)

    2011 F-150 Crew 4X4

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  7. #7
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    It will to a certain point but that is why I was saying to check the pressure.. When the motor is running with the AC on max at idle you dont want any more than 45PSI... That will be well over 120PSI with the system off... Your comressor will eat the bearings over 50PSI with the motor running... But the rear AC will be a bit colder since the majority of the pressure is sent to the rear before the front.
    Mike

    Currently

    1997 Chevy S-10 Blazer 4X4 with 330K miles and counting (Hunting rig).

    2009 Saturn Aura XE (wifes car)

    2011 F-150 Crew 4X4

    "Hold it to the floor till you see God.... Then Brake!!!!"

  8. #8

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    Quote Originally Posted by vicar75855 View Post
    Ok I am totally dumbfounded.... The back blows great right. Well after checking vac lines and other odds & ends I thought what the heck and added a can of 134a..... the front got cooler. How can the back blow cold on a common comp and the front need gas??? Is there something I am missing here? I added a second can of gas back still blowing cold front got cooler once again. If I wasn't seeing this I would never believe it.

    I am gonna grab some more 134 from town and add another can or so. Thanks for all the replies guys, try adding a bit of gas to yours it might make it work...

    Goodbye all from the Twighlight Zone....
    Don't add anymore refrigerant just yet.

    Please buy an AC pressure gauge from Your local auto store. They are basically similar to a tire gauge, though with readings specifically for an AC system.

    You can destroy many parts of the AC system by over pressurizing it, not to mention possibly harming yourself. Take Care!
    "I Hate When That Happens!"

  9. #9
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    My truck did the same thing and it was an orifice tube that needed replacing and the compressor and no more problems, the best I can say is stop wasting money and just take it to a shop and have them check it, especially with the suburbans and the massive A/C system that is in it.
    99 K1500 Suburban LT "THE BEAST"
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    Jason

  10. #10

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    The orifice tube up front is most likely stopped up.
    The lines for the rear A/C bypass that orifice tube, since the rear evaporator has its own expansion valve. This is why your rear A/C can blow freezing cold and the front can blow hot.
    Also, when you added the can of freon, you raised the pressure and basically forced freon through the clogged front orifice tube. This is bad, and can wash a lot of trash into the compressor.
    Take it in and have them replace the orifice tube and accumulator and do a complete flush and vacuum on the whole system. If it was bad enough to clog your front orifice tube, take no chances.

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