On my 98 Scenic RT Alize (with Air Con) the blower would only work intermittently on speeds 1-5 - full speed always worked fine and sometimes the lower speeds would stop and start working at random. I assumed this would be something to do with the resistor pack/thermal fuse but when I took the module out of the blower housing it turned out to be an electronic speed controller - instead of the resistors and fuse arrangement there was 2 massive TO-3 FETs (I assume) on a big heatsink. After taking it apart I found a problem with the soldered joints to the PCB from the connector so it was a pretty easy fix. Here is a short guide on what I did.
Firstly pop the tweeter covers off from each end of the dash and take out the torx screw on each side.
Carefully pull up the front edge of the dash till it pops off then slide it off forwards. Take out the torx screw and lift out the tweeter on the left side.
The big thing covered in foam above the glove box is a pipe going from the air distribution unit behind the centre of the dash to the left dash vent. Side the foam sleeve up into the middle so you can see the ends of the pipe. The ends are only a push fit but it's difficult to get them off. I started at the vent end, put my hand through the tweeter hole and popped the pipe off, the other end was then easy to get off and pull the pipe out. You can then see the control module held in with 2 screws (4mm head).
The unit is a big heatsink with a little control module at the top. To get the covers off the top you need to look for 2 little square holes in the black plastic at the top and use a small screwdriver to leaver the housing off the heatsink and then the other half of the housing clips off.
Looking very carefully at where the pins from the connectors were soldered to the PCB I noticed there was something up with joints (can just make this out in the pic below)- wiggling the connector confirmed this
To get a good solder joint I used a cheapo high-wattage iron, some decent solder and extra flux. I re-did all the pins for the connector and it now works perfectly
. Putting everything back together is just the reverse - I put the pipe back on at the vent end first.
Final thing to mention is the cabin (pollen) filter for my car was a Fram CF9818 - was a pain to get the right one at the local motor factors. Hope this info helps somebody!