Ferrari Testarossa 1990 A/C function | FerrariChat
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Ferrari Testarossa 1990 A/C function

Discussion in 'Boxers/TR/M' started by leslie_choo, Sep 24, 2023.

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  1. leslie_choo

    leslie_choo Formula Junior

    Aug 5, 2012
    444
    Singapore
    Full Name:
    BCChoo
    #1 leslie_choo, Sep 24, 2023
    Hi I am restoring my Ac unit , and I saw there is a AC cooling condenser and a heater coil . I would like to find out how does this function before I decide to NOT connect the heater coil ( due to I am in hot climate country ) . Can you pls help to confirm my understanding is correct ?

    Question - we need both AC and Heater coil in order for it to function correctly because the AC ECU is using the coolant valve to turn ON of OFF to adjust the flow of hot coolant into the system to adjust the desire temperature for the aircond . Ie if we adjust to 23 degree Celsius when the AC temp falls below 23 degree the ECU will off the valve so there is some hot coolant flow into the system to adjust it to hit 23 degree or ECU can also off the compressor if it falls too cold below 23 degree . Hence we cannot disconnect the coolant hose in the system if we want it to function correctly . Is my understanding correct ? Or if the heater and AC are 2 separate systems and not related when they operate ?
    Thanks


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  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    36,750
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    Brian Crall
    #2 Rifledriver, Sep 25, 2023
    The car does not have an AC system. It is a climate control system. It uses hot water and freon to regulate temperature.
     
  3. 71veedub

    71veedub Formula Junior

    May 31, 2006
    327
    Boston/North Shore
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    Greg
    #3 71veedub, Sep 25, 2023
    Right, it is an integrated HVAC unit, but he could block the coolant flow to the heater core or tie the valve shut if he never needs heat. I also have a 928, and that is sometimes done by owners in warm climates because the valve does leak a little hot water into the heater core, and can also fail. But in Massachusetts, US I do need working heat so not an option for me.
     
  4. leslie_choo

    leslie_choo Formula Junior

    Aug 5, 2012
    444
    Singapore
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    BCChoo
    #4 leslie_choo, Sep 26, 2023
    Thanks for the information . That’s right it’s a integrated HVAC system . The system uses both the coolant and refrigerant to regulate the A/C temp . I am wondering if i block off or disconnect the coolant from flowing the system , will it impact how the A/C ECU functions to regulate the A/C ? The A/C ECU will probably have to off the compressor if there is no coolant heat to regulate.

    The reason I ask is because the coolant water is leaking and the heater valve probably needs to be serviced too . (New heater coolant valve is very expensive )
     
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #5 Steve Magnusson, Sep 26, 2023
    Have you tried internet searching using the Bosch part number:

    Bosch 1147213007 (I believe it's also used on BMW and MB.)

    Also (unless the outside plastic housing is broken/cracked), this valve's internal parts can also be rebuilt -- try an internet search using "Bosch mono valve repair kit"

    One final note is that this hot water valve can only close properly if the coolant lines are hooked up so that the coolant flow matches the arrow on the housing. The shop that did my last major replaced the heater hoses and got them switched around -- took me a lot of effort to figure that out ;).
     
    71veedub, turbo-joe and Rifledriver like this.
  6. leslie_choo

    leslie_choo Formula Junior

    Aug 5, 2012
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    #6 leslie_choo, Sep 27, 2023
    Thanks Steve , I believe you refer to the coolant flow direction ? As per the picture below and I hope the picture below is correct ( follow the inlet flow arrow ) .

    Do you know how does this valve function? I assume during A/C cooling the
    A/C ECU will send 12v to ON the valve so that the valve will turn to close position and hence no coolant will flow through the outlet into A/C evaporator ? The ECU regulates the temp by adjusting the valve ON / OFF .

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  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,507
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    #7 Steve Magnusson, Sep 27, 2023
    Last edited: Sep 27, 2023
    Yes, that diagram of the hot water valve is correct. The pressure from the inlet flow helps keep the valve closed; whereas, if the hoses are hooked up backwards, the solenoid mechanism does not have enough force to keep the valve closed (so hot water always flows).

    Your description of the electrical function is also correct (except the hot water only flows in the heater core, not the evaporator, but, since the airflow passes thru both, your thought is correct). Also, when the "STOP" push button is pressed (with key "on") a constant +12V should be present between between the two wires at the hot water valve (to always hold it closed) so:

    If you wrongly get heat when the STOP push button is pressed with the engine running, and you don't have +12V between the two wires at the hot water valve (with key "on") = you have an upstream electrical problem.

    If you wrongly get heat when the STOP push button is pressed with the engine running, and you do have +12V between the two wires at the hot water valve (with key "on") = either the hot water valve itself is bad (bad internal seal or open solenoid coil) or the hoses are hooked up backwards.
     

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