E46 Climate Control Unit

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If your climate control is switching itself off or resetting then it is probably the control module itself which is faulty. Luckily there is a common fault which is easy to repair yourself using the information below. If you don't feel comfortable repairing it yourself and you are in the UK then I recommend you visit http://www.bmw-climate-repair.co.uk who offer a repair service for £35
If you find than the fan is not coming on or is coming on at a low speed then check to make sure the microfilter is not blocked. If it is not blocked or the fan problem is intermittent then it is probably the climate output stage which has failed. This is located behind the glovebox by the center console.

A good article about fixing the climate control module can be found at http://www.macadamizer.com/bmwfix.html

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I would recommend that a polyester capacitor be used instead of the tantalum capacitor mentioned because a tantalum has to be wired the correct way around. In the UK you can obtain the polyester capacitor from Maplin part code WW49D (Polyester Layer 0.47uF) cost 31p.

It is also advisable to remove the solder from the joints on the blue connector and resolder them as these joints breaking is another common fault with this module.


If the fan will not go above a particular speed and especially if this is intermittent then the fault is most likely the 'output stage'.

With manual heater controls there is a switch and the 4 outputs go to a resistor pack and through the resistors to the fan in order to control the speed. The pack is separate due to size and the fact that it generates a little heat.
On climate control the computer sends a signal to the output stage and this then switches on and off power to the appropriate resistor inside.


This difference is operation is why on manual heating the fault manifests in low fan speed settings the fan not coming on at all but on climate control it does not go above a certain speed.

I know the glovebox is removed to get access to the output stage and I think it is near the center console area. I don't have a picture of it or part number though.


Climate Control Module Pinouts

Bmw E46 Climate Control Unit Not Working

TypeConnects ToPurpose
OutputN2 Output StageOutput stage controls the speed of the fan
InputFuse 31Water valves, immobiliser, clock, instrument cluster etc..
InputFuse 23Rear demister, ABS etc..
InputStarterProbably to switch off the fan, demister etc.. when the car is being started
OutputM36 fresh air flap motorUsed to switch on and off fresh air from outside when using air recirculation button
GroundGround for control unit
Ground for flap motors
Ground for control unit
Input / OutputDiagnostic linkUsed to diagnose any climate control problems
OutputY4 left water valveOpens valve to allow hot water into the left heater matrix
OutputY4 right water valveOpens valve to allow hot water into the right heater matrix
InputLight switchAdjust display illumination when the car lights are on
OutputRear demister
OutputOn board computerEither the climate control unit or the on board computer can activate the independant ventilation relay
InputIndependant ventilation relayRelay controls power from fuse 20 going to this power input
B414 AUC sensorDon't know what this sensor is. Pins 2&3 connect to a sensor.
InputLeft heat exchanger sensorMeasures the temperature of the left heater matrix. This in conjunction with the set temperature is used to decide whether to open the left valve to let more hot water into the matrix
InputRight heat exchanger sensorSee above
InputOutside temperature sensor
InputEvaporator temperature sensorUsed to decide when to turn on and off the aircon compressor. If left on for too long the evaporator will ice up and therefore the temperatore needs to be maintained at a set level
InputInstrument clusterDiagnostic connector for climate control, instrument cluster, cruise control, immobiliser etc..
InputInstrument clusterTACH input indicating the speed of the vehicle


OutputB9508 pressure switchMeasures the gas pressure in the air conditioning system. If the pressure is too low the compressor will not be turned on

E46 Climate Control Unit Diagram

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