As per Ben1400's threads re the resistor pack, or as the Haynes Manuel calls it, the Heater Blower Motor Resistor/Control Unit, I've just repaired mine following Ben's instructions for his Laguna...what a top man!
As I have a 99 Scenic Alize with Air Con and I thought I would share with everyone who has the same (and it appears a commom ) problem, how I did this on my car - a much edited version of my experience!
Firstly, take out the pollen filter (if fitted) and the blower motor, then get upside down in the passenger footwell (in a girlfriend/mistress sort of stylee) and look up into the air chamber. You will see the resistor pack, but unless you're a gyneacologist, you won't have much of a chance carrying out the repair as per Ben1400's instructions.
Too get to the little beastie, I had to take off the top of the dash, straight foward and as per the Haynes Manuel. Once thats out of the way, you will seen the left hand air vent tube, its got a thin sponge cover. This has to be pulled from the centre consol air duckting and from the left hand air vent. It does come off, just needs a good 'yank'.
Underneath this trunking, you will then see the top of the resistor pack and you can now undo the little grub screw that hold the resitor pack into the air box. Once this is undone you can lift the resistor pack out and undo the electrical connections, 4 in total (3 on the top, one underneath the dash, to the blower motor) and repair it as per Ben1400 instructions.
The biggest of the 3 top connections ia a bit of a funny set up, as you will see a red ribbed 'tab' at one end. This simply pulls away from the main body and as it does so, it releases the connection.
The fuse is easily identified, as its the only one there, once you have replaced the thermal fuse, it all goes back together in reverse order. All in this took me about 3 hrs, but I have recently had the blower motor out and therefore managed it a bit quicker this time. If you can manage to see the resistor pack from the pollen filter 'hole', you don't need to remove the blower (this just gives you an idea where it is).
The replacing of the thermal fuse is straight forward as Ben states, it cost me the grand sum of 71p at Mapplins and thanks to Ben's fantastic input into the forum, not only did I save a fortune, I got a lot of satisfaction from repairing my own car!
JUST A QUICK UPDATE ON THIS THREAD, THE THERMAL FUSE I USED AS PER BEN1400'S INSTRUCTONS BLEW A DAY LATER (RATED AT 110c). I MANAGED TO FIND MY OLD ONE AND IT IS RATED AT 192c, MAPLINS PART NUMBER IS RA20W.......ITS STILL 71p!! This time I only took off the top of the dash and removed the heater tubing, all in it took me about 20-30mins, a real bonus.