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AC Issues 850 1994

It's summer time and everybody has ac issues! The compressor turns on and off every so many seconds continuosly never stoping as long as the switch is on. I charged the system to see if this was it. It hasn't helped any, only extending the time between cycles a few seconds. Any ideas?








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    AC Issues 850 1994

    If it's being switched on and off by the relay then it is normal control If it's being seitched on and off by the low pressure switch then your low on R34A.
    If you listen close you can hear the relay click behind the glove box. If you set the temp to lowest and operate everything in auto mode the clutch should stay engaged.
    --
    Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE








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      AC Issues 850 1994

      No, it is the low pressure switch that should be turning the A/C on and off (and in turn the relay). The A/C is SUPPOSED to cycle, it has to, just not too fast. Basically, as the compressor runs, it gets colder, which means the pressure inside the A/C system continues to drop. Once it gets to a certain point ~20 PSI, it shuts off until the pressure raises, to keep the evaporator from freezer (and also to prevent the compressor from running without lubrication which happens at low pressure). There's no set number of seconds it's supposed to cycle - depends on temp, fan setting, engine RPM's, speed, etc. But above 65 degrees while driving, it probably shouldn't cycle on and off more than every 6 seconds or so.

      Only if it's really really hot out would the A/C never cycle.








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        AC Issues Compressor Control 850 1994

        I stand corrected. Here is an excerpt from a service manual.
        ""A/C COMPRESSOR CLUTCH CONTROL
        The A/C compressor electromagnetic clutch is powered by the
        A/C relay. Compressor operation requires that the A/C relay be
        activated by both Electronic Climate Control (ECC) module and Engine
        Control Module (ECM). The ECM turns A/C compressor off when engine is
        at full acceleration, at high engine temperature, and for 5-10 seconds
        after starting engine.
        The ECC control module normally supplies voltage to A/C
        relay, except when heater (blower motor) fan is off and vehicle speed
        is less than 20 MPH, when heater fan is off and recirculation is on,
        or momentarily when under full acceleration.
        If A/C is switched off using the AC OFF switch, ECC control
        module will cut supply voltage to relay, turning off compressor.
        However, this does not apply when air distribution control is in
        defrost setting, since A/C is always on in this case.
        A/C PRESSURE SWITCHES
        The A/C compressor is connected in series with the lowpressure
        switch, high-pressure switch, and safety switch. The highpressure
        and safety switch cut power to the A/C compressor if pressure
        in the A/C high-pressure circuit becomes excessive, supplying a signal
        to ECM to start cooling fan.
        The low-pressure switch (pressostat) turns A/C compressor on
        and off to maintain pressure within limits.""
        --
        Tom 69-1800S, 72-1800ES, 96-850T,2000-S70 GLT-SE







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