Mondial 3.2 Cabrio 1987 HVAC - Relays | FerrariChat
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Mondial 3.2 Cabrio 1987 HVAC - Relays

Discussion in 'Mondial' started by aleib, Sep 27, 2023.

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  1. aleib

    aleib Karting

    Oct 12, 2022
    135
    Full Name:
    Alejandro Leib
    #1 aleib, Sep 27, 2023
    With the fan speed issue solved, now I would like to do something with the air, like cooling it or warming it :) the AC worked fine, but lost the pressue again, so will do a reparation (rebuild of the compressor if required).

    The heater should be simpler, but its not the case.

    I read several threads, but the diagrams shared are not compatible with what I have...

    I did a few test and noticed a something very important:

    with the 1st (driver side) relay removed, the lamp (installed where the heater valve goes) is OFF at full heat, BLINKING at medium settings and ON at full cold.

    I think this is a good sign of HVAC ECU working correctly rigth?

    when I install the relay back again, the lamp goes ON.. so no heat.

    whats wrong? I tried with normal relays (332 019 150) and crossed (332 209 150) ones but the effect is the same...

    Is my wiring stock? or it was modified by previous owner? (I will take a better picture later)

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  2. Alden

    Alden F1 Rookie
    Rossa Subscribed

    Apr 25, 2010
    3,402
    Central Florida
    #2 Alden, Sep 27, 2023
    I remember a thread from a long time ago from someone who was testing and replacing those relays and he said that the wiring diagram for those relays was incorrect, not sure what else was in his thread, but if you search a little you may be able to find it. Alden
     
  3. aleib

    aleib Karting

    Oct 12, 2022
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    Alejandro Leib
    #3 aleib, Sep 27, 2023
    yes i'm already diggin deep on this, and this looks bizzare, as the heater valve is operated by the HVAC ECU --> OR <--- the realy.

    when the AC is on, the relay overrides the HVAC ECU and turn the heater valve ON (no heat)...

    so it should not be THAT complicated to debug that bizzare situation.... unless the signal from the relay is used for another thing... but its very, very strange
     
  4. aleib

    aleib Karting

    Oct 12, 2022
    135
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    Alejandro Leib
    #4 aleib, Sep 27, 2023
    Fixed... the heater relay has 87a in the middle, not in the extreme!! So modified the socket and worked ....
     
  5. aleib

    aleib Karting

    Oct 12, 2022
    135
    Full Name:
    Alejandro Leib
    #5 aleib, Sep 27, 2023
  6. aleib

    aleib Karting

    Oct 12, 2022
    135
    Full Name:
    Alejandro Leib
    #6 aleib, Sep 28, 2023
    the conclusion here is:
    1) my harness was modified by previous owner (as SIPEA 0440 has 87a in the middle too) and the wiring diagram clearly shows that relay 87a goes to the heater valve
    2) the "heater valve realy" is not in control of the heater valve, the HVAC ECU controls the heater valve... its just an override to turn heat off (so turn the heater valve on) all the time while the internal fan is off... nothing more...
    I think it was the way to not complicate things on HVAC ECU... but that should be implemented there... and not this very complicated stuff...
     
  7. moysiuan

    moysiuan F1 Rookie
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    Nov 1, 2005
    4,106
    Canada
    #7 moysiuan, Sep 28, 2023
    The main failure item in the heater valve is the plunger inside. It is a spring loaded items with rubber seals. The seals fail, and or the plunger spring is not strong enough. This causes the valve to eg. Put out heat at idle, but as rpm rises and coolant preesure increase, the valve does not direct the heat to the heater as it should.

    There are replacement plungers, but they are not great quality, and the sropings can be too weak. The ones that used to cross to BMW parts are no longer available, they were the proper quality.

    The valve is solenoid actuated, and is in the always actuated position when the car is on and no heat is called for. The solenoid could stick or fail, but seems uncommon. It is possible for the internal spring valve to leak internally, and corrode or damage the solenoid.

    Making sure the relay works is important, because the valve is actuated when you start the car. The ecu controls releasing the voltage and allowing the plunger to be unenergized when called for heat. It is kind of the reverse of how one might expect the on off aspect would work.
     

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