HVAC unit intermittent operation | FerrariChat

HVAC unit intermittent operation

Discussion in '612/599' started by duxducis, Feb 6, 2017.

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  1. duxducis

    duxducis Rookie

    Nov 29, 2016
    25
    #1 duxducis, Feb 6, 2017
    Started to experience following problem on 599: After cold start, HVAC unit, below radio, does not turn on, no lights, looks like it is not connected at all. After 10-15 minutes of driving, short stop, turning the car off and starting again, HVAC unit start to operate normally.
    I have also noticed that sometimes, yellow lights, on temperature knobs, blinks few times. After this blinking and car restarting, HVAC unit start to work normally.

    Has anyone experienced similar problem or have idea how to fix this?

    Already searched 612/599 discussions, but did not find anything about this.
     
  2. duxducis

    duxducis Rookie

    Nov 29, 2016
    25
    #2 duxducis, Feb 9, 2017
    Last edited by a moderator: Sep 7, 2017
  3. swiss612

    swiss612 Karting

    May 10, 2016
    217
    Zurich
    Full Name:
    Michel
    #3 swiss612, Feb 9, 2017
    HVAC units have 2 bolts on the underpart, once they are out you have to pull the unit towards you as the back part is attached with metal pins, you have to pull hard as the pins are holding it well
    The thing I do not know on the 599 is how to access the bolts from the underside, I have done it on a 612 where it is obvious once you start looking under
    I usually look on ebay how parts are made and find where they are attached to the rest, unless you are sure, don't start as otherwise you'll break expensive parts...

    But are you sure that the AC control is the issue ?, is everything else in proper working order on the AC side ? I have not heard that these control units get faulty.
    How old is your battery ? I am asking because of the high current being drawn from the v12 at start up if your battery gets to too low voltage levels electronics will start to go wrong, this would explain that after a drive it is working properly, it happened with the Tire pressure monitor on my 612...
     
  4. duxducis

    duxducis Rookie

    Nov 29, 2016
    25
    #4 duxducis, Feb 10, 2017
    @swiss612

    Battery has been recently changed, but problem still persists.
    I suspect in some sort of loose connections.
    Those metal pins that you mention will be next thing to check.
    Official dealer connected car last week to the diagnostic tool, but could not find anything related to this problem. They also mentioned that most of the time it is cable connection problem, but I did not have time to leave the car for a few days, as my dealer is 500km away.
    So i decided to try to look up and solve the problem by myself.

    Thank you for the guidelines about how should I try to take out HVAC unit. I will certainly try that approach.

    Also did not hear or read that these units get faulty, but you never know.

    There is also AC ECU behind glove compartment box which can cause a problem.
     
  5. duxducis

    duxducis Rookie

    Nov 29, 2016
    25
    #5 duxducis, Feb 10, 2017
    One more interesting thing that should be mentioned:
    It happens after turning on battery master switch and follow procedures described in user manual and workshop manual, not to insert the key for 1 minute, than not to start the car for 30s after you insert the key and put it in position II, starting the car and let it idle for 10 minutes with everything else turned off. During that idle engine run, soon after the engine starts, ventilation starts to work, blowing the air inside the cabin, which becomes warm as the car warms up. HVAC controls are all turned off and unit does not show any sign of life.
    After 10 min of idle run, following with 5-10 min of drive and restarting the car, HVAC starts to work normal.
     
  6. swiss612

    swiss612 Karting

    May 10, 2016
    217
    Zurich
    Full Name:
    Michel
    #6 swiss612, Feb 10, 2017
    Hmmm... could be a bad connection but these things become rare on modern cars.
    There is a simple connector behind the HVAC control unit, spraying it with contact spray will do not harm, now the unit itself could be the cause, it can be opened but I have never done it, also there contact spray could help
    The ECU is an orange box in the passager footwell against the A pilar, you should not have too much to take out to access it and check connections, there is a small panel under the glove box that you can take out to change the cabin filter. on the 612 there are 4 screws holding it you will then see the orange box
     

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