Mondial t AC Compressor Clutch Electronic Weirdness | FerrariChat
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Mondial t AC Compressor Clutch Electronic Weirdness

Discussion in 'Mondial' started by alexx19, Jun 28, 2014.

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  1. alexx19

    alexx19 Rookie

    Jun 3, 2006
    21
    #1 alexx19, Jun 28, 2014
    Last edited by a moderator: Sep 7, 2017
    Bruce (aka Plugzit), Carl and I were charging the AC in my soon to be ex-Mondial t yesterday and are stumped by the opposite bizzaro world operation of the compressor clutch.

    >> the clutch engages the opposite time of when we'd expect it to

    Key On / Stop = Compressor clutch engaged (not running)
    Key On / Any Button (A/C, vent, defrost) = Compressor clutch NOT engaged but fan on (not running)

    This is the opposite of what you'd expect.

    Running car also shows the same results -- seems like the 62433300 PRESSOSTAT high/low pressure switch on the drier isn't part of this.

    Q1: How does this whole system work? i.e. what clicks the relay (or whatever) that supplies 12V to the compressor?

    NOTE: it seems this is a similar system to other cars of this era, specifically the 348, 512 TR and F40 all use this same 62433300 PRESSOSTAT according to Ricambi Ferrari Parts : 62433300 PRESSOSTAT : Ricambi America

    I will test the pressure switch, short across and see if there's anything new to report.

    I can't find any good schematics to look at but it seems that the switch does nothing other than turn the fans on and off. It's only 2 wires (of 3 terminals -- see pic) so it seems something else must be in the loop. Maybe the same switch operates stuff in the vacuum lines which operates something that operates the system that supplies power to the compressor clutch?

    Maybe we didn't get it vacuumed out sufficiently to get the right pressure and R12 in there?

    Q2: Any other ideas?

    ---

    Here's a link of some YouTube video from a company that repairs these: https://www.youtube.com/watch?v=-duZwoRtvOk

    From this video it seems that I've got all the wires in the right place.

    ---

    It seems this whole compressor clutch thing is wired to the ECU because it has to modify the idle when engaged.

    I'll look for the sender in this picture.

    ---

    Other things are that we just did a full engine out service so maybe some wire got bumped and before that I changed some of the switches in the dash so maybe I bumped something else.
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  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,839
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #2 Steve Magnusson, Jun 29, 2014
    Last edited: Jun 29, 2014
    (I'm responding here rather than to your email)

    I'm more familiar with the TR AC system than the 512TR AC system, but I reviewed the Mondial t schematics (they are in the Mondial t WSM that you can download from All Ferraris). The "PRESSOSTAT" is the high/low pressure switch (item 07130 on the schematic), and the easiest thing to do is just unplug it and then (using jumpers) connect all three wires in the connector on the harness side together -- this simulates a properly closed high/low pressure switch. If you still have compressor actuation trouble = the problem is elsewhere. If the compressor actuates OK = either bad high/low pressure switch, or your refrigerant charge is incorrect, or the system is blocked (one thing that you should do here is get the compressor running and look at the observation window on the Dryer -- if no refrigerant flow = bad/blocked -- and don't run the compressor long if it is blocked and the high/low pressure switch is bypassed). Good Hunting!
     
  3. alexx19

    alexx19 Rookie

    Jun 3, 2006
    21
    #3 alexx19, Jul 1, 2014
    Last edited by a moderator: Sep 7, 2017
    First, thanks for the detailed reply. ;)

    Did that - same result.

    So...

    Yep. So now the whole care is opened up. Bruce and I spent a lot of time studying the diagrams and testing things but still have this weirdness with no voltage or voltage at the wrong time to the pressure switch (and therefore the clutch).

    - the clutch engages when key on (no motor) and in STOP position
    - the clutch does not engage when A/C, A/E or Defrost is pushed
    - the clutch engages in STOP when the temperature sensor is set to cold but not when it's on the hot side

    I tested the potentiometer that controls the temperature and it tests out prefect. I even opened it up and checked inside -- there's no way to put the parts in incorrectly so that's done.

    The buttons (STOP, A/C, AE, Defrost) seem to work correctly as well -- it seems that wires are connected when any buttons are pushed and open when in STOP position. Only 2 of the 3 terminals are used -- the third terminal is open for A/C and STOP; closed for A/E and Defrost.

    I found a vacuum line that was a little bit crushed but fixing that did nothing.

    I opened up the Bosch 1 147 328 072 Control Unit for Air Conditioner Temperature Regulation (aka the brain) and it seems normal. The relay makes a funny noise when it actuates but that seems fine.

    The first problem seems to be that the green (Verde) V-1 wire is not being supplied at the right time -- I haven't traced all the logic yet but my current guess is that my problem has to do with one of the sensors reporting incorrectly to this box which shuts off the power delivery to the High/Low Pressure Switch and therefore the clutch on the compressor.

    PS I also noticed the problem where turning off the system, setting it to heat then turning on will give heat for 1 minute then it will get cold.

    Any thoughts from anyone? Anything else to check?
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  4. alexx19

    alexx19 Rookie

    Jun 3, 2006
    21
    #4 alexx19, Jul 1, 2014
    Last edited by a moderator: Sep 7, 2017
  5. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,839
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #5 Steve Magnusson, Jul 1, 2014
    Last edited: Jul 1, 2014
    You've got to get this fixed before worrying about anything else IMO. If you leave the AC ECU unplugged, does the compressor clutch still incorrectly engage with just the key "on" and the stop button pressed?

    A = microswitch 20
    B, F, and G = temperature sensors 19, 22, and 24. There should be instructions in the WSM about how to measure the resistance of each of these at the unplugged AC ECU connector (at the ambient temperature) to confirm/deny if they are OK or not.
    C = a timer to occasionally run the AC compressor when you have the defroster "on" (to help dehumidify the windscreen even if you are asking for heat). I don't see this in that parts diagram of the evaporator unit -- it might be the small black box between the silver box and the large black box in your photo (although they call this "timer for lights" on the footwell electrics SPC page). I would also unplug this item (if you can find it ;)) to see if it affects the problem of the compressor clutch incorrectly engaging with just the key "on" and the stop button pressed.
    D = the cabin blower motor
    E = one of the 27 relays -- this one closes to run the cabin blower at full speed when you turn the speed request knob to maximum speed
    H = the other 27 relay (IIRC, this one closes when you press any button other than STOP to send power to run the AC ECU).
    I = the 28 relay (a side note here is that the relay part number shown in that parts list, 40130106, is actually a substitute that can work OK, but it requires moving a wire in the corresponding relay socket as the 87a terminal on the original relay is in a different position vs the 87a terminal on that 40130106 relay). IIRC, this is related to the hot water valve operation (STOP button pressed = relay I not actuated = hot water valve always held closed; any other button pressed = relay I actuated = allows AC ECU to control hot water valve depending on whether asking for cooling or heat) -- so not related to compressor clutch troubles.
     
  6. alexx19

    alexx19 Rookie

    Jun 3, 2006
    21
    #6 alexx19, Jul 1, 2014
    Last edited by a moderator: Sep 7, 2017
    Yes, with any plugs disconnected and the clutch does not engage.

    Thanks for all the details regarding what those A-I components are. That was the secret key that I needed (along with the Italian color code) to figure out what was going on.

    Of course it took 6 hours of studying the schematics, making notes and putting it all together but...

    [size=+3]It is fixed![/size]

    It turned out to be something stupid :eek: -- after taking out each sensor, bring it upstairs and blowing with a hair dryer to test I moved along to figuring out where the relays were.

    Turns out that they are inside the passenger compartment and on the front firewall. There are 3 of them 2 of one kind and one of another -- I knew before pulling them out that this would be the issue. It was.

    It was my bad -- I was fixing the buttons for the trunk switches and thought these were part of the system so I took them off and cleaned the contacts. Of course I didn't put them back in the correct spot! What are the odds? 100%.

    <see last picture> The RED dot does mean something after-all; and I thought it was just some Forza Flag.

    -----------------------------------

    I am attaching a PDF with all the AC stuff, marked up and noted in case anyone ever needs to debug this system again.

    Thank you Steve! I'm buying you dinner if I ever make it to Texas!
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  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,839
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #7 Steve Magnusson, Jul 1, 2014
    Well, that was easy ;)

    Yes, if you wrongly swapped relay H with (the original) relay I, it would turn "on" the AC system when the STOP button was pressed...
     
  8. dfranzen

    dfranzen Formula 3
    Owner

    Aug 31, 2013
    1,577
    Ponte Vedra Beach , FL
    Full Name:
    Don Franzen
    #8 dfranzen, Jul 2, 2014
    this was great detailed info

    take away check relays first!

    thanks guys

    btw alex you really are fixing this mondi up for the new buyer!
     

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