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HVAC Problem S90-V90

posted by  1998S90 on  Fri Mar 13 10:01 CST 2015
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last visit: Fri Aug 2 07:15 CST 2013
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Hello, I have a 1998 S90. When I select the panel vent setting, it stays in heater/defrost mode for 10-15 minutes. When it finally decides to switch to the vents, there is a loud hissing noise as it switching. What's weird is, once it's in vent mode, accelerating does NOT affect the airflow, at least not that I can tell.

What are your thought on where to start looking and how to fix it.

Thanks in advance.








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    HVAC Problem S90-V90

    posted by  volvo426 on  Tue Mar 17 13:45 CST 2015
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    last visit: Thu Oct 23 13:44 CST 2014
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    If its like my 92 960 i had a few dry solder joints on the back of that valve plus the a/c controller in the dash had a few dry solder joints hit them with the iron and re ran the solder and all good.Symptoms were weird hissing noises as you described plus a hiss when you turned the car off you could here the vents moving.








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      HVAC Problem S90-V90

      posted by  1998S90 on  Wed Jun 29 13:19 CST 2016
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      last visit: Fri Aug 2 07:15 CST 2013
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      Turns out it was indeed a cracked solder joint that I hadn't seen before. I put some new solder on it and all is good. Thanks everyone for your responses.








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    HVAC Problem S90-V90

    posted by  hf63 on  Fri Mar 13 14:57 CST 2015
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    last visit: Wed Oct 22 15:19 CST 2014
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    On the passenger side behind the glove box, you will find a vacuum valve that controls all vacuum to the servos. When you make a change on the controller the valve controls the vacuum to each change.

    Check this valve.








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      HVAC Problem S90-V90

      posted by  1998S90 on  Tue Mar 17 12:37 CST 2015
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      last visit: Fri Aug 2 07:15 CST 2013
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      Thanks for the reply AF. I was in motorcycle safety class all weekend with my son but am now back and ready to takle this project. I was able to find the valve in question but I really don't know how to check it. It seemed to operate fine. It operated properly as I ran through the different settings. I unplugged the electrical connector and it defaulted to the heater/defrost position. Could there just be an intermintant gremlin inside the switch? Are those lines coming out of the top of the valve the vacuum lines?








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        HVAC Problem S90-V90

        posted by  machine man on  Wed Mar 18 01:02 CST 2015
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        last visit: Wed Oct 22 15:40 CST 2014
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        Hi there,

        I do not anything about these cars and was just plunking!

        FYI

        When you unpluged the unit, its default is to go to that condition for safety reasons. All cars, to the best of my knowledge, are made this way.
        Mechanically or Electronically, there has to be heat available to the occupants, if the car generates it.

        It is designed to fail to heat, that way, if you were in the cold, say a bilzard, you would not freeze to death!

        If you get too hot, then you can always roll down a window or just get out!

        Phil






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