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Air vents switch to defrost on hill climb - Heating & Cooling

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  • ccecliff Jul 19, 2009

    Already spent $98 to have 95 Lincoln Towncar checked out - no prob with check valve, or vacuum. They wanted to pull entire dash, to see if dirty or something - Wanted $1100. Any other suggestions?

  • ccecliff Jul 20, 2009

    Re vacuum line feed - No, haven't - trusted auto dealer that it was ok - I don't know where it is located. Just not willing to spend 1100 dollars on a car, that will retail for about that. If you can tell me how to locate, I'll try for sure (I never totally trust "parts replacers") Appreciate your come back tx

  • ccecliff Jul 20, 2009

    Best Ive heard so far - will try this, thanks

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Vacuum leak or faulty check valve in line to AC controls. What make , model , year , of vehicle?

Posted on Jul 18, 2009

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  • Mike Butler
    Mike Butler Jul 19, 2009

    Have you tried locating vacuum line feed yourself to dash controls?

  • Mike Butler
    Mike Butler Jul 20, 2009

    Normally you'll find a vacuum line connected to brake booster perhaps, that connects near bigger vacuum hose on booster, or in earlier years came right off intake manifold, but probably easiest thing to do is look at firewall area on drivers side, or mid way across, for a small black, usually hard plastic or rubber hose going into firewall that would be going to area of heater controls. If control panel not too hard to get out of dash, you can usually pull it out far enough to see or locate vacuum line coming in to back of controls. See if you can find anything & in the meantime, I'll see if I can get some more info on your particular vehicle & where it might be. Also, if you look under dash on passenger side to middle while you have engine running, and switch back & forth from & to defrost, you may hear where all that is going on, and find line in that area as well.

  • Mike Butler
    Mike Butler Jul 20, 2009

    Many vehicles including Lincolns, incorporate a fail-safe system so that if there is a drop in vacuum due to slight or large leak in system or any circuits (hoses) used, it will automatically go to defrost, in order to allow for clear windshield for driving. Yours would be the same, and from what I can find, it doesn't appear too difficult to pop front trim panel off around controls & remove screws to get access to rear of controls. Sharpen your hearing & listen for a small "hiss" anywhere under dash, behind controls etc, and you may just find it yourself. I purchased a vacuum gauge years ago, that I use, and I would put it in line coming to controls (main feed line in) and shut engine off & see if vacuum held, if it did, i knew up to controls was good, so my problem was either a leak at control itself, or one of the outgoing lines from control.

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