W208 Heater fan resistor

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stchris356

New Member
Joined
Dec 8, 2010
Messages
20
Location
Warwick
Car
W211 E500
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
 
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?
 
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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