Have just tackled this job on my wife's Scenic Mk2 2006, this one has the climate control option so the electronic fan control module rather than the resistor pack.
She has been complaining for the last few weeks that the fan was intermittent; sometimes not working at all and at other times running continuously regardless of the fan setting. It was most recently in this latter state and the blower fan could only be stopped when the ignition was switched off.
Went through the upper dash next to the display. Used mobile phone camera to take a pic inside the dash and Could just see the green plugs (there are two) on the module and one torx mounting screw. See photo.
As others have said, a pig of a job to get to. You have to rely completely on your sense of touch to undo the torx screw, remove the plugs and slide the module out because you cannot see anything once your hand is in the dash! Also tricky to get the torx screw out without dropping it.
I was rather surprised to find that the module itself was heavily corroded, see photos. Dated 01/2006 so is the original unit. I'm an electronics engineer so decided to have a go and repairing it.
Cleaned the PCB thoroughly with RS Solvent Cleaner and a nylon fibre brush, desoldered & removed the green socket and cleaned the PCB under that. Also removed the MOSFET from the heatsink, cleaned it and applied new thermal paste. Resoldered the green socket and resoldered all the corroded solder joints. See photos of before and after the cleanup job.
Very pleased to say that once the job was done and it was reinstalled the module is fully operational again.
A BIG thank you for the helpful forum posts on this subject especially how to get access to the module in the first place.
However - I am still concerned that this module has been getting damp in the first place. Obviously it is 8 years old so it has not been exposed to water on a daily basis so I'd imagine that it is due to condensation. I couldn't feel any moisture inside the dash during the work.
Does anyone think I should be also checking for a leak somewhere or is this normal for the Scenic?