A/C compressor control logic | FerrariChat
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A/C compressor control logic

Discussion in '456/550/575' started by Timmo, Aug 5, 2024.

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  1. Timmo

    Timmo Formula Junior

    Aug 26, 2017
    680
    Continental Europe
    #1 Timmo, Aug 5, 2024
    I searched the archives and the WSM with no answer to this question: when the A/C is running, is there an engine speed or any particular load condition (TPS > ? %, etc) over which the HVAC ECU orders to declutch the A/C compressor?

    I cannot believe that the A/C compressor can withstand the load he would be getting from sustained high speed cruising or the beating it would take from extensive track use.
     
    INRange likes this.
  2. INRange

    INRange F1 World Champ
    Silver Subscribed

    Jan 27, 2014
    12,554
    Virginia/Florida/Caymans
    Full Name:
    JD
    #2 INRange, Aug 5, 2024
    Modern automotive ACs are controlled by a shared or dedicated ECU. When the AC's clutch is ordered to engage....a signal goes to engine management to increase RPMs to compensate for the compressor drag. Conversely the compressor clutch can be ordered to disengage for a number of reasons including: TPS %, high compressor pressure, low compressor pressure, engine rpms or switching the system off.

    Older Ferraris used a STOP switch to turn the compressor OFF for aggressive driving.
     
  3. Qavion

    Qavion F1 World Champ
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    Feb 20, 2015
    14,297
    Sydney
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    Ian Riddell
    #3 Qavion, Aug 5, 2024
    I couldn't find any wires from the Motronic ECUs to the HVAC ECU (other than a wire telling the Motronic ECU that the compressor is running). There is a data line between the instrument panel (digital display unit) to the HVAC ECU, but tacho data doesn't seem to feed into the digital display unit.

    I guess there's always the max gas pressure limit of 25bar which cuts out the compressor.
     
    Timmo likes this.
  4. Timmo

    Timmo Formula Junior

    Aug 26, 2017
    680
    Continental Europe
    #4 Timmo, Aug 5, 2024
    Thanks Ian. It seems odd to me that the pressure in the circuit is the only input data used to declutch the compressor automatically.

    I guess the ECUs need to know if the compressor is engaged only to adjust idle speed due to the increased load.
     

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