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Fresh Air Fan Resistor Pack

  • 28-03-2022 5:58pm
    #1
    John.G
    Registered Users Posts: 3,464 ✭✭✭



    Decided to post on here as I reckon some excellent electrical knowledge on hand.

    Briefly, I have a 3 year old VW (polo) that has had 2 new replacement (under warranty) resistor packs, 3 in all with only ~ 14500kms total. I asked for investigation after second replacement but no joy so I decided to carry out a few tests today after removing the resistor pack. Should also say that these resistors are inserted in the fresh air fan ducting so are air cooled. The fan will only then run in speed 4 when the resistor pack fails. It will also run in speed 4 if your remove the pack terminal block.

    The pack is fed from the fan switch and the terminals are numbered 1 to 4 from right to left. The numbers below are self explanatory, but terminal 4 which in speeds 1,2&3 is the ground wire but becomes live (12V) when the fan is switched to speed 4, can someone give a explanation for switching this wire to Live, bearing in mind that the fan will run on speed 4 without any resistor pack or wiring harness and also any comments on the unacceptably very short pack life. (The pollen filter was changed).


    Polo Fresh Air Blower Wiring.docx


    image.png


    My Polo Resistance Pack..jpg




Comments

  • #2
    Shoog
    Registered Users Posts: 4,139 ✭✭✭Shoog


    These resistor packs have a built in thermal fuse which is probably what is failing. The reason it is likely to be failing is because the fan itself is catching and the excess current is blowing the resistor pack fuse.



  • #3
    John.G
    Registered Users Posts: 3,464 ✭✭✭John.G


    Polo Fresh Air Blower Wiring.docx


    image.png


    My Polo Resistance Pack..jpg


    No, not catching because you can turn the fan impeller quite easily with 2 fingers with filter removed.



  • #4
    John.G
    Registered Users Posts: 3,464 ✭✭✭John.G





  • #5
    zg3409
    Registered Users Posts: 6,546 ✭✭✭zg3409


    It seems to be a common faulty unit and the replacement also seems to be unreliable.

    The resistor pack is "bypassed" at full speed as it's not needed.


    Often certain cars or the parts have known issues and replacing the part with like for like is likely to cause the same issue down the road. Over time they typically bring out a new version that fixes the problem, however on cars with only 3 years warranty it soon becomes your problem.



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