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AC vents shut down during acceleration: FAQ question 900

posted by  rstarkie on  Sat Aug 25 15:37 CST 2018
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last visit: Fri Oct 24 10:14 CST 2014
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https://www.brickboard.com/FAQ/700-900/HeatingAirConditioning.htm#960ACVentStopsWorkingUponAcceleration

In this section of the FAQ's it talks about plugging the vacuum line to the servo to eliminate the problem of the dash vent outlets from shutting down. It points out that this also eliminates the recirculating cab air.

I find both of my 94 940T sedans have what can only be described as marginal AC systems. If I eliminate the ability to recirculate the cabin air and use outside temperature air I pretty much would have to give up trying to cool the cabin.

So does anyone see the plugging of the vacuum line any kind of a real fix?

Thanks, Randy







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    AC vents shut down during acceleration: FAQ question 900

    posted by  tedv on  Thu Aug 30 18:12 CST 2018
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    last visit: Sat Oct 18 10:51 CST 2014
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    This is usually caused by the one way valve (usually black/white in color) in the vents line at the fire wall allowing vacuum to escape back under acceleration. Cheap part.








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      AC vents shut down during acceleration: FAQ question 900

      posted by  rstarkie on  Sat Sep 1 20:17 CST 2018
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      Thanks for your response, but the one way valve is in fact functioning properly.

      I'm trying to determine if giving up the recirculation function (after plugging the vacuum line to the servo) will render the AC useless because it will be trying to cool the cabin with outside air- which might be 90 degrees.

      Randy








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        AC vents shut down during acceleration: FAQ question 900

        posted by  jwalker on  Sun Sep 2 06:06 CST 2018
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        last visit: Fri Jun 6 08:39 CST 2014
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        You are doing the right thing. Keep researching. Maybe someone here knows for sure. I too would not give up the recirculate function. Older Volvo’s AC systems are too weak to overcome the lack of a recirculate function.
        --
        Will I buy another Volvo??? We'll see....








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          AC vents shut down during acceleration: FAQ question 900

          posted by  Paulii on  Wed Sep 12 18:36 CST 2018
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          you need to pull the a/c panel and use a vacuum pump like a mighty vac and test each of your vacuum lines to the vacuum servo, white is supply, orange is recirc, I forget the other colors off hand but you test each one and the one that doesn't hold the vacuum is the problem. Replacing them can be a challenge. I replace them all on the 960's now, the servo's are getting a bit pricey, but you don't want to do the job again when the next one goes out. It also gives you a chance to clean the evap and remove all the dirt and dust that has accumulated in the air box Lube all the door hinges with a good silicone grease,








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    AC vents shut down during acceleration: FAQ question 900

    posted by  1pocket on  Tue Aug 28 09:12 CST 2018
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    yes, pinching off the yellow vacuum line does work and the after effects are the cabin will still cool down even under acceleration.

    what no longer will work is air circulating from vents down by your legs

    if you want perfection remove and fix it.

    as for recirculating cabin air i have no idea if the fix does or does not restrict this feature which is immaterial to cooling the cabin down







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