Bad solder joints are common on the resistor, the flow microswitch often goes intermittent then fails. You need to use a voltmeter to find the break in the electrical circuit, do so with care as the thing is live, and use a earth leakage breaker in the supply if at all possible. It could be the fan bearings are sticky, try some wd40 on them (not a long term solution). Actually working on the fan is meant to be a corgi job as it is inside the sealed chamber.
c
February 2010