Question about 1997 GMC Jimmy

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Ac cotrols stuck in vent mode

Ac controls stuck in vent mode. no vacuum to control head. where does vacuum line tap into under the hood?

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  • schochiometr Aug 24, 2008

    No changes to fuses. I rechecked all fuses and they're good.

  • schochiometr Aug 25, 2008

    To clarify, I have a 1999 GMC Jimmy, 2 wheel drive. I checked for vacuum at the ac/heater contol and there is no vacuum. I found where the vacuum line comes out under the center of the dashboard to the left of the console. It runs back to the firewall and into a large wire bundle. I can't see where it goes from that point. I've looked under the hood at the firewall and can't see the vacuum line. I'm trying to find the vacuum source to determine what the problem is. Is there a switch or relay I'm not aware of? I have a Haynes manual but it's no help for this problem.

  • schochiometr Aug 25, 2008

    ac controls stuck in vent mode. no vacuum to control head. where does vacuum line tap into under the hood?
    Comment by schochiometr, posted on Aug 24, 2008
    No changes to fuses. I rechecked all fuses and they're good.
    Comment by schochiometr, posted on Aug 25, 2008
    To clarify, I have a 1999 GMC Jimmy, 2 wheel drive. I checked for vacuum at the ac/heater contol and there is no vacuum. I found where the vacuum line comes out under the center of the dashboard to the left of the console. It runs back to the firewall and into a large wire bundle. I can't see where it goes from that point. I've looked under the hood at the firewall and can't see the vacuum line. I'm trying to find the vacuum source to determine what the problem is. Is there a switch or relay I'm not aware of? I have a Haynes manual but it's no help for this problem.

  • schochiometr Sep 02, 2008

    Please review my last comment. I need info on the vacuum hose origination point. Perhaps you can provide me with a vacuum hose diagram. I have no vacuum to the ac/heater controls.

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Double check the compressor as well. Have you checked and clean the air filter? Also check any leak even the slightest leak can affect. Overheating also affects the vacuum. You can also try flushing the lines, evaporator and condenser using flushing equipments.

Posted on Aug 25, 2008

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ac cotrols stuck in vent mode - 6869vacuumdiagram.jpg check this diagram.and locate the vaccum line.

Posted on Aug 25, 2008

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Check the vacuum hose at the intake, just next to the compressor. line is broken, and that line goes near the heater box under the hood,and also look for a ground wire on the front passenger side on the radiator support arround the head light it could be also be a culprit.

Hope this may help;

Regards,
VOTIT

Posted on Aug 25, 2008

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Sir,

the vacuum line can be found under your kick panel which is located above where your feet would go when you were driving. It is held on with 3 torx screws. Once they are removed it will pop right off. You might have to do some fishing for the line but its a black vacuum line and its up there. I believe it has a T connection in it. You should also consider that it might not actually be the vacuum line. It could be the actual gauge itself.

Thanks
good luck

Posted on Aug 24, 2008

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Did you made any changes to the fuses lately.

Posted on Aug 24, 2008

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