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A/C Control Problem

Discussion in '308/328' started by Sheldon Rubin, Aug 28, 2009.

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  1. Sheldon Rubin

    Sheldon Rubin Rookie

    Jul 10, 2006
    37
    #1 Sheldon Rubin, Aug 28, 2009
    My '83 Mondial QV A/C blows cold and my heater works fine. Problem is that I cannot adjust the Temp Control to a setting that enables the Compressor to cycle ON and OFF. Instead it cycles from COLD air to HOT air; then COLD air ...... So I have to continually cycle the A/C manually by depressing the control buttons. Has anyone had any problems with the Bosch Control Unit which is located under the passengers footrest panel? The pot (variable reistance potentiometer) that controls the temperature is good. If I could locate a wiring diagram for the A/C I could trace it out.
     
  2. Lawrence Coppari

    Lawrence Coppari Formula 3

    Apr 29, 2002
    2,192
    Kingsport, TN
    Full Name:
    Lawrence A. Coppari
    #2 Lawrence Coppari, Aug 28, 2009
    I had a 1980 Mercedes 450SL that would switch from cold to heat, then back to cold. In my case it was a bad transistor on the control board. The board had two transistors that got pretty warm when operating in AC mode. One transistor was breaking down when hot. I found it by pulling the board and connecting it with a bunch of wires so I could hold it in my hand. When it screwed up I'd give it a squirt of freon. It immediately would switch to AC mode again, then reheat and screw up again. I replaced the transistor.

    Your mileage might vary......
     
  3. Paul_308

    Paul_308 Formula 3

    Mar 12, 2004
    2,345
    #3 Paul_308, Aug 29, 2009
    AC wiring diagrams (http://www.ferrari308gtbi.com/) do NOT show
    a special temp control in the footwell.

    The AC has two controls. On/off - temp on the left and AC Fan speed on the right.

    The left control temp will cycle the ac clutch on/off depending on the temperature of the evaporator via a long tube which goes forward into the AC area (near the brake master cylinder). So, yours may be operating normally unless that tube is broken. Sorry can't remember the name of it.
     

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