When you get to the switch you will find that it is an inexpensive standatd slide switch avaliable at Radio Shack.
You will probably find that the switch is OK and that brittle plastic parts that slide the switch off and on are broken.
To get the Electrolux Model 90 open for repair:
1) Open the bag door and remove the bag.
2) Pull off the rubber side moldings.
3) Pull forward on the plastic (probably white) slide strips that held the rubber side moldings. Completely remove them. Mark them left and right for reassembly. They are not reversable.
4) Lift straight up on the top half of the outter shell.
5) The two self tapping screws closest to the bag end release the entire switch assembly. Use caution removing the screws. The blue plastic and the clear plastic can be very brittle after a few years.
Bob Sherrill, September 2007