Recently our L322 has developed a clicking sound in the cabin on unlock of the doors. This sound was originally quiet but more recently has become very pronounced. It only happens when the car in unlocked after a period of more than 5 minutes. You unlock the doors and enter the cabin to be presented by a loud, ticking/ clicking noise for 8 seconds.
Following some investigation we narrowed this sound down to coming from the steering wheel area and internet sources suggested part of the a/c system at fault. It is actually the hvac heater blender motor or mechanism at fault. (part number ECB515). This motor is located in the left of the drivers side footwell under the steering wheel. Remove the side panel trim (one hex head screw) and pulls out directly from clips running down the left edge.
This reveals the motor which is to the right of the ducting and held in with clips and one screw (if memory serves). Remove this motor and carefully pull out the wiring harness to disconnect. Open the offending part (sep. motor from gearbox using clips which are present) and apply some gun grease or similar high grade grease to the workings of the gears. Be careful because as you remove the motor from the gearbox there is a tiny gear which sits on a pin which runs across from gearbox housing to motor housing (ensure this pin and gear are located properly on reassembly). If gearbox will not turn when apart from motor or motor does not work (when it is still wired to the truck) replace motor.
If it all seems ok just grease and reassemble. You will note the motor turns a plastic fin which in turn moves a wheel. You can see this wheel as it is revealed on the truck when you take out the offending part. You can turn the wheel with your finger by reaching up into the cavity where the motor was. It looks like a criss cross of plastic fins set within a 1 inch plastic pipe. This is because the fin on the motor / gearbox sits within these fins and turns the pipe / fins within thus adjusting the airflow. Apply some grease to this wheel as well and make sure it turns but remember to line up the fins so the motors plastic fin sits nicely in the recess.
Having moved all the parts I was worried it may be mis-calibrated on reassembly but my system seemed to work ok with no more clicking noises. I hope yours does to!