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Aircon/High-speed fan issues (long post)

Discussion in 'MK1 & MK2 Toledo' started by Kaloyan Nikolov, Aug 21, 2019.

  1. Kaloyan Nikolov

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    Hello people,
    I would be very happy if someone try to help out here, because we're running out of options, and sorry if my English is not good enough.

    Car symptoms (tl;dr) : No A/C at all, climatronic not engaging A/C compressor.

    Things done to the car in several services and / or specialists :
    1) A/C compressor inspection, oil and magnetic clutch replacement (they was not that bad, but we had the compressor out anyway)
    2) A/C condenser replacement with new one.
    3) A/C pressure switch replaced with new one. (old one measured with oscilloscope, it seems working, but we replaced it anyway, see below)
    4) R134a refrigerant refill, after a fairly decent leak tests.
    5) Manual engaging both the radiator fans and clutch of A/C from car battery, system works as it should.
    6) Control box under the car battery replaced with new one, after trying out several others second hand, with the same OEM number. I have (several) a working second hand one(s) as spare(s).
    7) Control unit inside dash temporary replaced with a new working one, returned the original since A/C did not turn on.

    Additional tests that has been done:
    0) Full fuse inspection - everything both inside and outside fuse box without problems, no burned areas, no blown fuses, voltage as expected, no heating when fans are manually engaged.
    1) Wire test from the box under the car battery to the climatronic unit inside the dash, according to the schematics from both auto-data and tolerance data - both wires between the units work fine (can add images of schematics if needed). No shortcuts, no resistance on wires.
    2) Manual engaging the A/C system to measure pressure - it was OK.
    3) Full scan of the car with VCDS - apart from several errors that was not related to a/c system - no problems / no errors.
    4) Manual measuring of the sensors for both inside / outside temperature - they are ok
    5) Verifying values of temperatures - they match the readings with vcds.
    6) Heated the car enough to trigger fans - they work on slow speed. Cooling system is decent, so i cannot heat it with the engine running and get to the second speed (without risking engine overheat). Accepting ideas on this one.
    7) Removed plug from radiator thermosensor and bridged the connectors to test the speeds : slow speed working, fast speed not working!
    8) Separated the fan connection on the lower side of the fan assembly, applied battery voltage to the connectors - both slow and fast speed of the bigger fan working, smaller one have only one speed and it's working - assuming fans are OK.
    9) Tested the Fresh air intake duct temperature sensor (G89) - it is working, also it does not show error in VCDS on that one.

    What could be possibly wrong? The only other idea i have is to take out half the front of the car, and test wire by wire everything, and measure every single (f!#@!#) connector.


     
  2. Smileyman

    Smileyman Active Member

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    some years ago - with a different make of car - I had a problem with the heating system, the fan only worked on the fastest speed. Turned out it was the fan resister that had failed, a common problem. Not sure if this is your problem but worth checking - if only to cross off the list!

    Good luck and do come back to let know how you got on.
     
  3. Kaloyan Nikolov

    Joined:
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    Hello, and thanks, but both speeds work fine.
     

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