Things You'll Need
Socket wrench set
Small pry bar
Over time, the motor pulley on an evaporative cooler can begin to wear out and warp. When this happens, it can make the pulley squeak and create more problems for the unit. It's not difficult to replace the pulley; it can be done in about an hour. The pulley is attached to the motor shaft with a set screw and can be swapped out using a few common tools.
Turn the breaker switch for the unit off at the breaker box before you begin. Close the shut-off valve to stop the water supply to the cooler.
Remove the cooler's back panel by lifting it up and away from the unit. Loosen the bolts that secure the motor to the motor mount with a socket wrench. Do not remove the bolts; just loosen them enough for the motor to slide forward on the mount.
Take the belt off the motor pulley. Loosen the set screw on the pulley shaft between the pulley and the motor with an Allen wrench. Remove the pulley from the shaft and set it out of the way.
Attach the new pulley to the motor shaft, tightening the set screw with the Allen wrench and place the belt around the new pulley. Apply tension to the belt by pulling back on the motor with a small pry bar. Tighten the bolts that secure the motor to the motor mount with the socket wrench.
Attach the cooler's back panel. Turn the water back on at the shut off valve. Flip the breaker switch back on.
To avoid electric shock, never attempt to replace the pulley on an evaporative cooler while the breaker switch for the unit is still on.