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A/C reduction on acceleration adjustable? 900

posted by  Mr. Weekend on  Sat May 27 21:42 CST 2017
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My 1996 960 air conditioner seems to to go from cold air to hot air almost instantly when I push on the gas pedal. I've had cars that cut the airflow off when you accelerate hard (RX-7), but it never blew hot air. Is there a way to adjust this feature, or disable it completely?








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    A/C reduction on acceleration adjustable? 900

    posted by  Amarin on  Sun May 28 03:28 CST 2017
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    last visit: Thu Oct 23 22:42 CST 2014
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    Hi Mr Weekend,

    Fairly speaking I've never heard of this "AC turn off during acceleration" feature for RWD Volvo cars. For some other cars with small displacement engine yes I've heard about it but not for Volvo. It is to gain more acceleration by cutting off some engine load.


    For the usual RWD Volvo AC setup, possible causes could be:

    1) System a bit low on refrigerant. The low pressure pressostat (at accumulator) switches off the system when it detects lower than usual pressure during acceleration. Check your AC pressure with manifold gauges. Recharge if needed.

    2) Increased clutch gap than spec - usual symptom is when engine still cold the AC is OK but hot air blows when engine is hot. Increased gap may also cause less clutch grip during acceleration thus mimics as if the AC is off. Check your clutch gap. General specs should be between 0.4mm to 0.6mm.



    Regards,
    Amarin.








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      A/C reduction on acceleration adjustable? 900

      posted by  Mr. Weekend on  Sun May 28 15:17 CST 2017
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      Hi Amarin! I will indeed service the a/c, it is probably low on refrigerant.








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        A/C reduction on acceleration adjustable? 900

        posted by  jimo on  Sun May 28 18:13 CST 2017
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        last visit: Thu May 8 10:43 CST 2014
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        Your problem is most likely related to a vacuum leak where one of your vacuum valves looses vacuum and opens a flap causing you to get hot air.
        Try putting the fan on position 1 and turning off the radio and when you accelerate and then let off the glass, listen to see if you hear one of the vacuum valves.
        Also check under the hood to see if there is a vacuum leak on one of the hoses that go thru the firewall on the passenger side for the air conditioning.There are some little valves in the hoses just before the hoses go thru the firewall that could be bad. They are about 3/4 inch long and white on one side and black on the other. They let the air move one way through the valve and not the other way so that when you accelerate and the vacuum drops, you will not loose your cool air.
        But one thing for sure is that you should not loose the cool air on your V90 when you accelerate.
        Jimo








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          A/C reduction on acceleration adjustable? 900

          posted by  Mr. Weekend on  Mon May 29 06:38 CST 2017
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          Thanks, Jimo, that makes a lot of sense! I'll check it later today.








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            A/C reduction on acceleration adjustable? 900

            posted by  Mr. Weekend on  Mon May 29 19:05 CST 2017
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            Okay, this is weird. I haven't been using the a/c until today, but I turned it on to check it per Jimo's suggestion, and the a/c stays on even under hard acceleration! The only change that has been made is the replacement of the brake booster assembly. Could I have had a leaking check valve on the old booster?








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              A/C reduction on acceleration adjustable? 900

              posted by  jimo on  Mon May 29 20:05 CST 2017
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              last visit: Thu May 8 10:43 CST 2014
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              The brake booster leaking would be a big vacuum leak and even if you had other small leaks, replacing the booster and having a big leak fixed could make all well with possible other small leaks. If it is now working well-go with it.

              Jimo








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      A/C reduction on acceleration adjustable? 900

      posted by  Michael Yount on  Sun May 28 11:37 CST 2017
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      last visit: Thu Oct 23 20:03 CST 2014
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      Agree w/Amarin -- usually, there's a simple wide-open-throttle switch that kills the compressor clutch when you're under full throttle. Otherwise, the A/C should work all the time. Diagnose the problem.....something's wrong with A/C function unrelated (likely) to the operation of the engine.








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        A/C reduction on acceleration adjustable? 900

        posted by  Mr. Weekend on  Sun May 28 15:14 CST 2017
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        Thanks, guys! I would have sworn I read about that feature in the owners manual, but I can't find it. The former owner may have mentioned it. Anyway, the status quo isn't acceptable, so i will be doing some troubleshooting. It is definitely related to throttle position, anything past light throttle affects the a/c, so I may have a bad sensor somewhere. The engine runs GREAT, and the a/c works well otherwise.







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