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R134a system pressures

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  • R134a system pressures

    My system has been converted to r134 for many years. Now it is not blowing as cold as it used to. I have the manual and the temp/pressure graph for r12, but wondered if the pressures were different for r134.
    I have a manifold gauge to use but want to accurately use the readings.
    Thanks.
    Bill Z

  • #2
    Hi Bill
    On my gauges- Low side 15-20 psi on a normal warm day while holding the revs at around 1500, you should see the gas bubbles clear out and disappear in the receiver dryer sign glass. On a hot day I sometimes have a garden hose available to spray the condenser to cool it down to see if the sight glass clear out and the low pressures come down to 15-20 psi.

    I dont know what the high side runs at I do everything through the low side.
    Dave.


    E30 M3 1987
    Mini Clubman GT
    BMW E36 323 Msport
    Toyota Corona
    KTM 200EXC
    Honda CB50 (1979)

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    • #3
      Well at 2000rpm I was getting at most 34 psi low side, 225 psi high side with center vent at 64 F*. This at 90* ambient.
      To my thinking, normal low and low high side equals bad compressor.
      I do not know if they are NLA but will look into it
      it is cool enough at present so won’t do anything soon.
      Thanks

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      • #4
        Originally posted by lsupcar View Post
        Well at 2000rpm I was getting at most 34 psi low side, 225 psi high side with center vent at 64 F*. This at 90* ambient.
        To my thinking, normal low and low high side equals bad compressor.
        I do not know if they are NLA but will look into it
        it is cool enough at present so won’t do anything soon.
        Thanks
        This post helped me a lot when i was working on my A/C:

        http://www.bimmerforums.com/forum/sh...roubleshooting

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        • #5
          Search for: Nominal Air Conditioning System Pressures R-12/R-134a technical article from BMW.

          B 64 13 92 (3646) Woodcliff Lake, NJ
          Product Engineering
          October 1992

          This site will not allow a .pdf upload.

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          • #6
            Thanks everyone.
            Couldn't find the BMW technical article though.

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