Climate Module Repair

Climate Module Problems

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 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

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.


Fan Speed Problems

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.

Technical Info

Climate Control Module Pinouts

Pin Type Wire Colour Connects To Purpose
19 Output BL/RT N2 Output Stage Output stage controls the speed of the fan
25 Input RT/GE Fuse 31 Water valves, immobiliser, clock, instrument cluster etc...
24 Input GN/GE Fuse 23 Rear demister, ABS etc...
9 Input SW/GN Starter Probably to switch off the fan, demister etc... when the car is being started
Output WS
M36 fresh air flap motor Used to switch on and off fresh air from outside when using air recirculation button
Ground BR
Ground for control unit
Ground for flap motors
Ground for control unit
26 Input / Output WS/VI Diagnostic link Used to diagnose any climate control problems
18 Output GE/VI Y4 left water valve Opens valve to allow hot water into the left heater matrix
13 Output GE/BR Y4 right water valve Opens valve to allow hot water into the right heater matrix
7 Input GR/RT Light switch Adjust display illumination when the car lights are on
12 Output BR/GE Rear demister  
8 Output SW/WS/GE On board computer Either the climate control unit or the on board computer can activate the independant ventilation relay
20 Input GN/BR Independant ventilation relay Relay controls power from fuse 20 going to this power input
X1558 1
X1558 2
X1558 3
B414 AUC sensor Don't know what this sensor is. Pins 2&3 connect to a sensor.
3 Input GE/RT Left heat exchanger sensor Measures 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
4 Input BE/BL Right heat exchanger sensor See above
1 Input BL Outside temperature sensor  
2 Input GR Evaporator temperature sensor Used 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
6 Input SW Instrument cluster Diagnostic connector for climate control, instrument cluster, cruise control, immobiliser etc...
5 Input SW/WS Instrument cluster TACH input indicating the speed of the vehicle
1 ?
2 ?
3 ?


M35 defroster flap motor
M44 ventilation flap motor
M46 foot and rear flap motor
M40 circulation flap motor

Used to open and close the flaps controling ait to the windscreen, center vents, foor vents and the recirculation function respectivly.

Maybe the AUC sensor controls these? Pin 3 is labled as M-Bus

10 Output VI/GR DME control unit Labled as 'Speed increase'
11 Output BL/SW B9508 pressure switch Measures the gas pressure in the air conditioning system. If the pressure is too low the compressor will not be turned on
Colour code Colour
BL Blue
BR Brown
GE Yellow
GN Green
GR Grey
OR Orange
RS Pink
RT Red
SW Black
VI Violet
WS White
TR Transparent