How to Inspect the Idler Pulley
A belt loops around the drum, under the idler pulley and over the drive pulley on the motor. The idler pulley (also called a tensioner) consists of a wheel on a movable bracket attached to a spring or tension bracket. If the idler pulley does not function properly, it can result in a loose belt that slips or fails to turn the drum at all. Also, the pulley wheel itself can make a squealing noise as result of a failed bearing. If the wheel does not turn at all, it can result in friction with the belt resulting in a burning odor and damage to the belt.
Before inspecting the idler pulley, unplug the clothes dryer or shut off the power at the fuse box or breaker panel to avoid an electrical shock hazard.
Access to the idler pulley varies by model, if your dryer has a lower front panel (kick plate) start there. It should lift up and off or it may be held in place with a few screws or snaps; it may also have a catch at the edges or center gap between the kick panel and main panel. To release the catch, push a putty knife, wrapped with masking tape, into the gap and push back the catch. The next easiest access point is the rear panel. The rear access panel is held in place with several screws along the outer edges. The last resort method of access is the removal of the entire front panel. The front panel supports the front of the drum and so removal is more difficult. Front panel removal varies. In general, access is gained by lifting the top (remove the lint trap screws first), removing the screws that secure the front panel, and detaching the panel from the drum.
When reaching into the dryer be careful of sharp edges on the cabinet and interior supports. Reach in to the belt and give it tug. It should be taught and have only a little give. The belt should go under the idler pulley and over the motor pulley. Lift the idler pulley toward the motor to relieve tension on the belt and remove it from the motor pulley.
Turn the idler pulley wheel, it should turn smoothly, quietly and without any wobble. Inspect it for cracks or uneven wear. If the idler pulley does not maintain proper tension or is damaged it should be replaced. Depending upon your model, the entire assembly or just the wheel or bearing may be replaced.