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a/c starts out cold, then heats up

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  • sheetfar
    I have a 1986 528e. What would cause the air conditioning to work fine for about 15 minutes or so, then start heating up slowly? This occurs under the
    Message 1 of 5 , Jun 14, 2004
      I have a 1986 528e.

      What would cause the air conditioning to work fine for about 15
      minutes or so, then start heating up slowly?

      This occurs under the following conditions:
      * Air vents closed (no outside air leaking in).
      * Temp switch set to coldest (rotated CCW).
      * A/C fan speed set to medium or high (2 or 3).
      * Outside temp above 90 deg F. (It doesn't seem to act up until the
      outside temp is hot).
      * Inside air vent (vent above radio) temp starts out at 42 deg F,
      then slowly works its way up to maybe 55 deg F.

      What I did so far:
      * Replaced the expansion valve on the evaporator.

      The low & high side pressure readings seem ok (20 or so psi low
      side, and 225 high side. The compressor seems ok, since it cycles
      off at around 335 psi when the engine revs up. All the gage readings
      appear to be normal.

      The heater control valve is working fine.

      I heard that the evaporator temp sensor on the earlier models could
      cause icing under certain conditions (Bentley). One parts supplier
      mentioned the possibility of a bad temp regulator.

      Any thoughts?
    • Ron Kall
      A/C problem - you did not mention how old the freon was? this car is R12. some not so good shops have been know to put R134a into these R12 systems instead. i
      Message 2 of 5 , Jun 14, 2004
        A/C problem - you did not mention how old the freon
        was? this car is R12. some not so good shops have been
        know to put R134a into these R12 systems instead. i
        watched my guy dump 3 lbs. into mine in a shop in LA
        and I made sure it was R12. Good work and cold as ice.
        older systems get looser and leak. belt slippage on
        the compressor pump as the engine heats up? a/c can
        cease to be cool if airflow goes down - stuck in
        traffic or stopped, but mine would always get colder
        as i went longer and faster. good luck.

        Ron Kall

        1986 528e
        1985 535i

        --- sheetfar <sheetfar@...> wrote:
        > I have a 1986 528e.
        >
        > What would cause the air conditioning to work fine
        > for about 15
        > minutes or so, then start heating up slowly?
        >
        > This occurs under the following conditions:
        > * Air vents closed (no outside air leaking in).
        > * Temp switch set to coldest (rotated CCW).
        > * A/C fan speed set to medium or high (2 or 3).
        > * Outside temp above 90 deg F. (It doesn't seem to
        > act up until the
        > outside temp is hot).
        > * Inside air vent (vent above radio) temp starts out
        > at 42 deg F,
        > then slowly works its way up to maybe 55 deg F.
        >
        > What I did so far:
        > * Replaced the expansion valve on the evaporator.
        >
        > The low & high side pressure readings seem ok (20 or
        > so psi low
        > side, and 225 high side. The compressor seems ok,
        > since it cycles
        > off at around 335 psi when the engine revs up. All
        > the gage readings
        > appear to be normal.
        >
        > The heater control valve is working fine.
        >
        > I heard that the evaporator temp sensor on the
        > earlier models could
        > cause icing under certain conditions (Bentley). One
        > parts supplier
        > mentioned the possibility of a bad temp regulator.
        >
        > Any thoughts?
        >
        >





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      • Gerald Paul
        Don t forget about maybe needing to add oil with your freon charge. ... __________________________________ Do you Yahoo!? Friends. Fun. Try the all-new
        Message 3 of 5 , Jun 14, 2004
          Don't forget about maybe needing to add oil with your
          freon charge.
          --- Ron Kall <ronjkall@...> wrote:
          > A/C problem - you did not mention how old the freon
          > was? this car is R12. some not so good shops have
          > been
          > know to put R134a into these R12 systems instead. i
          > watched my guy dump 3 lbs. into mine in a shop in LA
          > and I made sure it was R12. Good work and cold as
          > ice.
          > older systems get looser and leak. belt slippage on
          > the compressor pump as the engine heats up? a/c can
          > cease to be cool if airflow goes down - stuck in
          > traffic or stopped, but mine would always get colder
          > as i went longer and faster. good luck.
          >
          > Ron Kall
          >
          > 1986 528e
          > 1985 535i
          >
          > --- sheetfar <sheetfar@...> wrote:
          > > I have a 1986 528e.
          > >
          > > What would cause the air conditioning to work fine
          > > for about 15
          > > minutes or so, then start heating up slowly?
          > >
          > > This occurs under the following conditions:
          > > * Air vents closed (no outside air leaking in).
          > > * Temp switch set to coldest (rotated CCW).
          > > * A/C fan speed set to medium or high (2 or 3).
          > > * Outside temp above 90 deg F. (It doesn't seem to
          > > act up until the
          > > outside temp is hot).
          > > * Inside air vent (vent above radio) temp starts
          > out
          > > at 42 deg F,
          > > then slowly works its way up to maybe 55 deg F.
          > >
          > > What I did so far:
          > > * Replaced the expansion valve on the evaporator.
          > >
          > > The low & high side pressure readings seem ok (20
          > or
          > > so psi low
          > > side, and 225 high side. The compressor seems ok,
          > > since it cycles
          > > off at around 335 psi when the engine revs up. All
          > > the gage readings
          > > appear to be normal.
          > >
          > > The heater control valve is working fine.
          > >
          > > I heard that the evaporator temp sensor on the
          > > earlier models could
          > > cause icing under certain conditions (Bentley).
          > One
          > > parts supplier
          > > mentioned the possibility of a bad temp regulator.
          > >
          > > Any thoughts?
          > >
          > >
          >
          >
          >
          >
          >
          > __________________________________
          > Do you Yahoo!?
          > Friends. Fun. Try the all-new Yahoo! Messenger.
          > http://messenger.yahoo.com/
          >





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        • ken@kenholyoak.com
          Just went through this today. Found AC to work sometimes and not work at other times. The refrigerant has been R12 with 134 added along the way. Then sealed up
          Message 4 of 5 , Jun 14, 2004
            Just went through this today. Found AC to work sometimes and not work at
            other times.



            The refrigerant has been R12 with 134 added along the way. Then sealed up
            with silicone to stop a leaky valve.



            Local AC man did great job converting the old R12 to a new 134 system and
            cost $150 including parts. Done inn two hours.



            Kenneth. H. Holyoak

            Information + Insight = Profit

            POB 68633

            Indianapolis, IN 46268-0633



            ken@...

            317-253-7000



            -----Original Message-----
            From: Ron Kall [mailto:ronjkall@...]
            Sent: Monday, June 14, 2004 3:31 PM
            To: bmwe28@...
            Subject: Re: [bmw e28] a/c starts out cold, then heats up



            A/C problem - you did not mention how old the freon
            was? this car is R12. some not so good shops have been
            know to put R134a into these R12 systems instead. i
            watched my guy dump 3 lbs. into mine in a shop in LA
            and I made sure it was R12. Good work and cold as ice.
            older systems get looser and leak. belt slippage on
            the compressor pump as the engine heats up? a/c can
            cease to be cool if airflow goes down - stuck in
            traffic or stopped, but mine would always get colder
            as i went longer and faster. good luck.

            Ron Kall

            1986 528e
            1985 535i

            --- sheetfar <sheetfar@...> wrote:
            > I have a 1986 528e.
            >
            > What would cause the air conditioning to work fine
            > for about 15
            > minutes or so, then start heating up slowly?
            >
            > This occurs under the following conditions:
            > * Air vents closed (no outside air leaking in).
            > * Temp switch set to coldest (rotated CCW).
            > * A/C fan speed set to medium or high (2 or 3).
            > * Outside temp above 90 deg F. (It doesn't seem to
            > act up until the
            > outside temp is hot).
            > * Inside air vent (vent above radio) temp starts out
            > at 42 deg F,
            > then slowly works its way up to maybe 55 deg F.
            >
            > What I did so far:
            > * Replaced the expansion valve on the evaporator.
            >
            > The low & high side pressure readings seem ok (20 or
            > so psi low
            > side, and 225 high side. The compressor seems ok,
            > since it cycles
            > off at around 335 psi when the engine revs up. All
            > the gage readings
            > appear to be normal.
            >
            > The heater control valve is working fine.
            >
            > I heard that the evaporator temp sensor on the
            > earlier models could
            > cause icing under certain conditions (Bentley). One
            > parts supplier
            > mentioned the possibility of a bad temp regulator.
            >
            > Any thoughts?
            >
            >





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            [Non-text portions of this message have been removed]
          • sheetfar
            I have also tested the aux fan (the electric fan located at the very front of the car) by shorting the wires for the sensors at the top of the radiator per
            Message 5 of 5 , Jun 15, 2004
              I have also tested the aux fan (the electric fan located at the very
              front of the car) by shorting the wires for the sensors at the top
              of the radiator per Bentley. Result: The fan works at both speeds.

              I then turned the ignition switch on but didn't start the engine.
              With the ignition on and the A/C switch turned on (the compressor
              clutch engaged), the aux fan then started at low speed. Conclusion:
              The aux fan ain't the problem.

              That leaves the evap temp SENSOR and the evap temperature REGULATOR.

              I removed and tested the temp sensor (it goes inside of the
              evaporator) at room temp and in ice water. Results suggest it isn't
              faulty.

              About the only thing left as far as I can tell is the temp
              regulator. And that would make sense, since the A/C sometimes acted
              up more than at other times. In other words, this regulator would
              probably be more likely to fail with time, since it has a lot more
              electronic devices inside (like those miserable SI boards).

              -Russ


              --- In bmwe28@..., "sheetfar" <sheetfar@w...> wrote:
              > I have a 1986 528e.
              >
              > What would cause the air conditioning to work fine for about 15
              > minutes or so, then start heating up slowly?
              >
              > This occurs under the following conditions:
              > * Air vents closed (no outside air leaking in).
              > * Temp switch set to coldest (rotated CCW).
              > * A/C fan speed set to medium or high (2 or 3).
              > * Outside temp above 90 deg F. (It doesn't seem to act up until
              the
              > outside temp is hot).
              > * Inside air vent (vent above radio) temp starts out at 42 deg F,
              > then slowly works its way up to maybe 55 deg F.
              >
              > What I did so far:
              > * Replaced the expansion valve on the evaporator.
              >
              > The low & high side pressure readings seem ok (20 or so psi low
              > side, and 225 high side. The compressor seems ok, since it cycles
              > off at around 335 psi when the engine revs up. All the gage
              readings
              > appear to be normal.
              >
              > The heater control valve is working fine.
              >
              > I heard that the evaporator temp sensor on the earlier models
              could
              > cause icing under certain conditions (Bentley). One parts supplier
              > mentioned the possibility of a bad temp regulator.
              >
              > Any thoughts?
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