W208 Heater fan resistor

Discussion in 'Electronics' started by stchris356, Oct 3, 2011.

  1. stchris356

    stchris356 New Member

    Messages:
    18
    Joined:
    Dec 8, 2010
    Location:
    Warwick
    Car:
    CLK 230 KOMPRESSOR
    OK, My heater fan stopped working but does work from time to time.
    I purchased a new resistor, fitted it and the fan ran perfectly on all speeds, brilliant I thought until I came out the next morning to discover a completley flat battery.
    Attached jump leads to find the fan constantly running.
    If the ignition is turned on the fan then operates normally but when the ignition is turned off the fan also goes off............for about 30 seconds(just enough time to allow you to get out of the car and lock it!!) and then comes back on and flattens the battery overnight:doh:
    Any ideas or is it a faulty new resistor?
    Thanks
    Chris
     
  2. Ted

    Ted MB Club Veteran

    Messages:
    5,639
    Joined:
    Feb 26, 2004
    Location:
    Bourton on Dunsmore
    Car:
    SLC 250D AMG Line, Yamaha XVS 1100, Jeep Renegade
    Unlikely to be the resistor.
    Sounds more like you may have fitted it incorrectly (backwards) or it is touching a live terminal. Does the problem fix itself when you remove the resistor?
     
  3. Alex Crow

    Alex Crow Hardcore MB Enthusiast

    Messages:
    278
    Joined:
    Sep 30, 2011
    Location:
    Super Suffolk
    Car:
    S210 320cdi
    the 'resistor' is actually a regulator, it uses pulse width modulation to control fan speed.

    it has 3x wires, permanent live, permanent earth and signal wire from the climate control module.

    check the signal wire with a multimeter as you run the fan through its speeds to get an idea of the control signal, then turn the ignition off and watch the meter and see what happens.

    my guess would be a faulty regulator, they are £164 +vat from MB, so perhaps you have used a cheap one from elsewhere?
     

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