Heater Diagnostic Interpretation Help? | FerrariChat

Heater Diagnostic Interpretation Help?

Discussion in 'Mondial' started by moysiuan, Oct 3, 2020.

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  1. moysiuan

    moysiuan F1 Rookie
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    #1 moysiuan, Oct 3, 2020
    Last edited: Oct 3, 2020
    My Mondial 3.2 heater appears to no longer give cold a/c, nor is the heat when on as hot as it could be. I have reasd other threads about the heater valve and various sensors.

    The heater valve gets its 12 volts and clicks when it connector is taken on and off, so I think the solenoid is fine. I did the lightbulb hookup test, and it gets the 12 volts when the settings are off position, with the heater on there is no light regardless of the potentiomter setting. So I moved on to test the sensors and pot as per the WS manual at the connector to the ac control unit in the passenger footwell.

    When I did the ohm tests per the WS manual on the 6 pin connector, I am getting readings as follows:
    Spec at 22C
    1-2 21.4K ohms 11.4K Much Higher resistance
    1-3 22.2K ohms 3.2K Much higher resistance
    1-4 11.1oK ohms 11.1K On Spec
    1-5 11.2K ohms 0 to 10K will not respond to turning the potentiometer
    1-6 21.2K ohms 10K Much Higher resistance

    I presume the tests are done with the ignition off, and heater controls in the off position?

    I find it odd that the various sensors are not reading to spec, and the potentiomter is not functioning, all a coincidence? I am checking the various wiring connectors and such to find an issue, everything looks in order so far.

    The 1-4 reading means my in car temp sensor is fine.

    The 1-2 and 1-3 reading suggest failed heater and evap temperature sensors, and the 1-5 plus the light bulb hookup test indicate my potentiometer control has failed. I don't know what the 1-6 reading means.

    Anyone able to interpret what is going on here? Failed fuse box where the brown connector goes? It looks ok, but I am not sure how to test for some sort of problem in the fuse box?

    I would rather not chase down sensors and the pot assuming coincidental failure of all three until I am sure it is not something else?
     
  2. mike32

    mike32 F1 Veteran

    May 13, 2016
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    Do u have the wiring diagram ?
     
  3. moysiuan

    moysiuan F1 Rookie
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    Yes, I do. I am just perplexed by the odd readings Various connectors look clean and tight, I am not finding any obvious reason for a few readings to all read higher resistance. I have looked at old threads, mostly for the QV (mine is a CH88 3.2), and it does not look like anyone has had the problem I am noting.

    Will take the console apart, and measure the pot right at the control, and bypass any wiring issues as a start.

    With the pot, the movement from 0 to 10,000 ohms that one expects, is this reading from hot to cold or cold to hot?
     
  4. mike32

    mike32 F1 Veteran

    May 13, 2016
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    Re the water valve for the heat, i think i would take it out and put a water supply to it , check the water flow and solenoid operation.
    With all the funny readings i would look at the connection strips for the wiring first.
     
  5. moysiuan

    moysiuan F1 Rookie
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    I wonder if the sensors are covered in dirt. Can they be safely cleaned with electrical contact cleaner? How does one remove the eg heater temp sensor, I can't even figure out how to remove the connector, it seems locked on in some way. Does the sensor just pull out of the plastic heater box housing, or does it twist fit in there in some way ?
     
  6. mike32

    mike32 F1 Veteran

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    You have too many problems, all of a sudden. Loss of supply volts or lower volts to the control side ?
     
  7. moysiuan

    moysiuan F1 Rookie
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    Pot tests out fine when checked directly. So does the hot temp sensor (which just pulls out of the heater housing). So this is something in the wiring.
     
  8. mike32

    mike32 F1 Veteran

    May 13, 2016
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    About 5 connection blocks in the wiring, good place to start
     
  9. moysiuan

    moysiuan F1 Rookie
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    By cleaning every connector, I seem to have things working again even though everything looked clean and tight - but now the ac switch won't actuate the defrost and recirc flaps. Once asgain inspecting things, but can't find any issues. Maybe all my electrical on off for testing and such has shorted the ac pushbutton mechanism?
     
  10. mike32

    mike32 F1 Veteran

    May 13, 2016
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    That switch is like gold dust to find, there was a thread about it several months ago. Real odd internals and not available if i remember right.
     
  11. moysiuan

    moysiuan F1 Rookie
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    No worries, since it runs off of vacuum, and I had been using the controls for testing things, the vaccuum had depleted. Once the cars started up and the vacuum was replenished, all was working as it should.

    (I do have a spare switch I purchased years ago)
     

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