The Electrolux canister has a rocker switch that wears out with use. There is a switch button on the outside of the canister; underneath the switch button is a plastic rocker that sits in a groove. The switch button pivots "On" and "Off" in this groove. The Electrolux switch actually makes a clicking sound when the button clicks on or off. If there is no click sound, then the rocker piece needs replacing. You might hear a broken piece of the rocker rattling around in the nozzle of the vacuum. The spring mechanism under the switch can also prevent the switch from working.
Push down on the release lever for the bag opening on the canister and pull out the two bumpers inside the canister with pliers. These two bumpers give you access to the rear housing of the canister vacuum. Do not remove the motor from the canister.
Tilt the canister vacuum so it lies on its side. Remove the front bag door from its hinge. If necessary, write down how to put it back on after the repair.
Feel for the spring-loaded lockout switch inside the canister. The switch sits in the bag housing; it does not sit on the motor or on the cord rewind. Six Phillips screws hold the switch in place. Use a screwdriver to remove the screws from the bag housing and the switch.
Lift the housing and turn it at a 45 degree angle, the maximum distance it can go, and check the rocker to make sure it isn't broken. Look at the spring to determine if it is stretched, worn or missing. The spring to look at is the U-shaped spring underneath the switch button, not the rocker spring.
Check the rocker to see if it is broken. Remove the rocker from the housing; remove the rocker spring at the same time with needle nose pliers. You only need the pliers to remove the spring; the rocker will pop off the spring on its own. Use a cotton swab to rub some petroleum jelly on the new rocker before you insert it into the housing. The petroleum jelly lubricates the plastic so it slides on and off with little resistance.
Reattach the bag housing by reversing the 45 degree angle, installing it back-to-front. Reinsert the two bumpers and the front bag door. All the parts must align for the vacuum to work. If something doesn't fit right, it could mean that the previous piece wasn't reinstalled properly. Trace your work and redo where necessary.