The switches on the 501 hand vacs are inserted into the hollow handle grip, the clearance is very tight. First, remove the nut holding the switch into the handle tube, then remove the rubber grip, you might need to soften it with a hair dryer. Once the grip is removed, you might need to take the 4 screws off the handle that holds it onto the body of the hand vac, you also might need to switch the toggle into the on or off position to let it slide out of the tube, it is a pain in the neck job, but can be done.