Been having a strange clicking noise in my L322 for the last few months and its been driving me crazy. Its sounds like an electrical relay clicking on and off and seems to be coming from a number of places at the same time, behind the climate control unit and somewhere in the back of the car. It happens completely randomly once the car has warmed up.

Anyway today I finally found out what it is. When pressing the window child lock button on the drivers side door control panel it makes exactly the same noise. Upon investigation the rear drivers side window can only be operated from the switch on the drivers door if the child lock is on and lit. When off and in usual mode the window does nothing. Its almost like its backwards.

Anyone know what this could be? Seems quite a strange gremlin.

EDIT: Actually after a bit more playing around there is definitely something faulty with the rear drivers side door. The switch on that door is very intermittent when raising and lowering the window. It seems that by putting the child lock on in the front, it cuts out the rear switch from working and then works fine from the front. Does this sound like a faulty switch or would it be a regulator or a motor or something?

If you turn on the window lock In the front drivers window panel it is meant to disable the rear windows, hence the "child lock" feature

Also another ticking noise once the car warning up could be the Fuel burning pre heater, the pump on them is quite noisy and you can hear the tick tick tick of it whilst it's running.

Depends if you have a TD6 or a petrol model ?

Thanks hippo but the drivers door switch is the one that isn't working as it should. I can only use it to open the rear window when the child lock is on, otherwise it doesn't work. The other switches on the drivers door operate all other windows no matter if the child lock is off and on.

The rear door switch only works sometimes with all child locks off too. The clicking is definitely related too and looks to be the relay in the window switch pack switching on or off due to the problem.

A few hours searching and it looks as if plenty if people have had the same problem but always don't post how it was fixed.