Before you mess with the switch just cut the plug and six inches of cable from the end of the cord - throw it away and fit a new plug. Easy - quick - cheap and fixes lots of vacuum cleaner will not turn on problems.
Why? The wires snap inside the cable from constant tugging. - You may indeed have a defective switch but for the sake of 10 mins work and a 50p plug it might be an easy no-risk fix.
Good luck...
Peccavi, July 2013
