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Struggling with Heater Valve / Heater Control Testing. Super stumped.

Discussion in 'Mondial' started by Albert Penello, Mar 10, 2020.

  1. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Afterburner what test would you suggest? Is there another way to confirm the buttons are working properly other than what I just did?
     
  2. afterburner

    afterburner Formula 3
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    Jun 20, 2008
    2,130
    Hong Kong
    Did you test directly at the unit = eliminating any other wiring issue?
     
  3. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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    No. When any of the pushbuttons is pressed (other than STOP) only one electrical thing happens -- the GV wire at the pushbutton unit is connected to ground. This turns "on" the interior fan system whose operation is completely independent from the HVAC ECU and the heater valve relay.
     
  4. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Yikes. So it's strange that in my car, the AC Button acts the same as Stop. What could be causing this?
     
  5. Steve Magnusson

    Steve Magnusson F1 World Champ
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    You might have some other internal problem, but this video from Norwood shows the phenolic "sliders" inside the switch can break and need replacement:



    Does the "feel" of your A/C button seem a lot different than the other buttons?
     
  6. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    It doesn't - the whole system is feeling dry.

    Funny story, I took the car out for a drive and the AC button was pressed and the light was ON with no fan. Then, suddenly, the light went OFF and the fan turned on.

    A lot of things on this car are coming back as I drive it.

    Once I get the HVAC ECU sorted, I'll spend time on the button unit. It shouldn't affect the ability to get the heater and AC diagnosed I don't think.
     
  7. afterburner

    afterburner Formula 3
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    Jun 20, 2008
    2,130
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    Albert, the switch in the push button unit is easy to bypass. Just disconnect it and add a temporary switch instead with 2 wires.
    The you have no questions about it while diagnosing the rest.
     
  8. mike32

    mike32 F1 Rookie

    May 13, 2016
    2,615
    Uk
    That is a neat fix
     
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  9. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Agree -- my only minor criticism would be that bare aluminum "sliding" against bare aluminum maybe isn't so good, but once the modification is made to make it able to be disassembled that makes it much more serviceable, if necessary, and they may last a long time anyway as this is not a high-cycle situation. Since the sliders are water jet cut that would give an almost unlimited option for the slider material (assuming the right thickness material can be obtained), and there may be more modern plastics with much better strength and toughness than the original phenolic but with better frictional properties than the aluminum. Or an alternating slider stack of aluminum-modern plastic-aluminum-modern plastic...to not have any metal-to-metal sliding. Just some random thoughts that a good modification can evolve as new materials become available...
     
  10. mike32

    mike32 F1 Rookie

    May 13, 2016
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    If you could understand how it works, there must be a more modern way to do the same with the 3 buttons. I was following this thread on the fix but it was getting more complicated than my knowledge.
     
  11. greatscott73

    greatscott73 Karting

    Sep 1, 2017
    185
    West central Florida
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    Howard Scott
    I notice that video is about 9 years old. I wonder if they are still performing this service.
     
  12. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Ditto!
     
  13. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    Well, everything is now in working order for those following along. The A/C button is now working as expected (from pressing the button a lot!) and more importantly the heater knob is working great! (there is no AC as the unit is empty, but that's another story)

    My friend was able to diagnose the unit, create a full schematic, and recreate all the inputs on a bench. Once he replaced the OPAMP chip, all is working well.

    Funny story - the OPAMP chip he replaced it with was date coded 1984, so actually period correct! He had that part in his stash which he thinks he bought in college!

    One last note from a diagnosis perspective - the signal from the heater pot is relative to the signal coming from the interior temperature sensor. So although you might expect the light to blink all throughout the range, turning OFF at full heat and ON at full cold, that won't necessarily be the case. We noticed as the car warmed up (and the interior became more warm) the blinking ON and OFF would change at different times across the range. It's also pretty slow to respond so you have to give it a second.

    Lastly thanks again everyone for the help. My friend is going to list all the Part Numbers for each of the components within the schematic, and then I'm going to release the complete schematic to the forum. Perhaps Urs can add this to his already fantastic wiring diagram for future reference. My buddy believes that a skilled electronic hobbyist should be able to to recreate this entire unit from off-the-shelf parts vs. spending hundreds (or thousands) for a new unit. Maybe that can help future owners.

    Thanks again everyone for the help!
     
  14. afterburner

    afterburner Formula 3
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    Jun 20, 2008
    2,130
    Hong Kong
    Thanks for the update Albert - nice to hear things are working out.
    I would very happy to include the ecu schematics and parts list into my diagrams, which I am sure will help other owners having their car's HVAC perform as intended.
     
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  15. ronfrohock

    ronfrohock F1 Rookie
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    Aug 16, 2004
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    That’s awesome! And it’s also so nice to see the greater Mondial brotherhood band together to help you out.


    Sent from my iPad using FerrariChat.com mobile app
     
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  16. Cafe racer

    Cafe racer Rookie

    Mar 22, 2020
    18
    London
    Full Name:
    Nigel Waterfall
    Does anyone have a wiring diagram for the heater/AC system - my wiring is a real mess in the centre console & i suspect there's a few wires missing, especially on the switch for AC/Heat.

    I have a workshop manual, it has everything except what i need, if anyone has any pictures or info it would be a great help, the temperature sensing seems to work as i can hear relays operating when i move the temperature control, the fan speed switch is operating the relay in the footwell but the fan doesn't run (guess that's the transistor?)

    Any information (especially drawings) would be great
     
  17. Albert Penello

    Albert Penello Karting

    Jul 21, 2019
    159
    Woodinviille, WA
    Full Name:
    Albert J Penello, Jr.
    PM Urs (afterburner above). He sells a color PDF that is absolutely mandatory to deal with electrical issues.
     
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