My handle switch was intermittent in the power brush setting. Your guide helped me to get the handle apart. I was able to clean the switch with contact cleaner and restore it to operation for now. If it happens again, the next step would be to remove the switch from the circuit board and re-solder it in reversed. It is possible that the contacts that were formally used in the off position will be in better shape and function to energize the brush. ...unless the sliding contacts are shot too.

I've been able to keep this vacuum going for about a decade now.