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940 A/C Question (not a leak) 900 1994

posted by  someone claiming to be 850 owner on  Sat Jul 5 08:19 CST 2003 [RELATED]

Hello everyone,

I have a question regarding the A/C Charge. I have a '94 944 with 175k miles on it. It appears to have the original compressor. The air blows cool (not COLD), and I suspect the compressor is getting weak. I plan on replacing the compressor next summer, but for now, I'd like to know if anyone knows the ideal pressure level for R-134a. Right now I am running it a bit low at 23 psi, as my 854 has best performance with lower charge levels. The car holds a steady charge so I don't suspect a leak. And, can anyone tell me if air in the system will make a large difference in cooling capacity? There may be air running around in the system as well, as I didn't purge the cans when charging. Thank you for your advice everyone! By the way, it blows cold at highway speeds and cool (almost heading towards warm) at idle.








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    940 A/C Question (not a leak) 900 1994

    posted by  chris herbst on  Sat Jul 5 08:46 CST 2003
    Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
    last visit: Mon Oct 20 20:32 CST 2014
    [RELATED]

    By pressure, do you mean compressor cut-off pressure?

    You can get that down to very low 20s, if not a flat 20. But that's achieved by adjusting the cycling pressure. The low pressure readings are not good for determining charge pressures, though.

    If you're talking about high pressure side, that's going to be difficult to fin dout, because the factory 134 systems aren't equipped with means to check those pressures. You have to charge by weight into a non-leaking system for best results.

    Not purging the air from the hose when you charge is not the worst thing. One thing that is bad, is not vacuuming the system. A tiny bit of air won't kill it, but charging at atmospheric pressure is not very good. It'll still cool, but it will never cool very well.
    --
    Chris Herbst, near Chicago.








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      940 A/C Question (not a leak) 900 1994

      posted by  someone claiming to be 850 owner on  Sat Jul 5 14:26 CST 2003 [RELATED]

      Thanks Chris, your responses are always very detailed and prompt. By pressure I meant R-134a charge but then I hear pressure is a terrible way to measure the charge volume. There's a local shop that will do a vacuum and recharge for $20, and they are a MBZ/Volvo/BMW specialist. Hopefully that will help some for now, as I have never evacuated/recharged the car since I got it. I'll post the results in case anyone out there is interested.








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        940 A/C Question (not a leak) 900 1994

        posted by  chris herbst on  Sat Jul 5 15:11 CST 2003
        Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
        last visit: Mon Oct 20 20:32 CST 2014
        [RELATED]

        Twenty bucks?! Don't waste time taking advantage of that deal!

        Yes, low side pressure is not a good way to measure charge. High side pressure is an ideal way to measure charge, but that isn't an option on the 134a factory systems from Volvo, at least in most of the RWD product. You only have the discharge & recharge-by-weight method to use. Not the best way, but it's effective. Unfortunately it isn't very good for DIY maintenance, unless you're good with weighing things (and have a vacuum pump).
        --
        Chris Herbst, near Chicago.








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        940 A/C Question (not a leak) 900 1994

        posted by  Leon on  Sat Jul 5 14:56 CST 2003
        Author: [PROFILE] [EVERY POST] [THREADS] [BEST POSTS] RSS Feed     [IGNORE ALL POSTS]
        last visit: Fri Mar 28 12:49 CST 2014
        [RELATED]

        Have you cleaned the condensor and radiator. With 175K, they are probably stoped upand restricting air flow.
        --
        Leon Ramseur in NC, 1997 855, 1995 945, 1990 760, 1990 740 & 1990 745. 90 740 & 745 FOR SALE.







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