Electric motors use a solid shaft to transmit energy to the driven device. Fans, belts and pumps are examples of driven devices operated by an electric motor. The solid shaft runs through the center of the motor and rides on bearings at each end of the shaft. The bearings reduce the amount of friction on the shaft and help keep the shaft centered in the motor housing. These bearings require periodic lubrication to reduce friction and keep the bearings from burning up, resulting in a motor failure.
Shut the motor down and allow it to come to a complete stop.
Grease the motor bearing while the motor is warm. The heat built up inside the motor during normal operation will loosen existing grease in the bearing cavity, making it easier to displace with new grease.
Remove the grease relief plug from the motor bearing housing. The relief plug mounts near the bottom of the housing. It allows for excess grease or pressure to vent from the bearing housing while applying new grease.
Clean out the grease relief port with a pipe cleaner. Old grease becomes dry and hard inside the relief port. Break up the hard grease with a pipe cleaner and open the vent to allow a path for excess grease or pressure to vent.
Wipe the grease fitting clean with a clean, lint-free cloth. A light oil spray may help to break up hardened dirt and grease that accumulated on the grease fitting. Cleaning the grease fitting fully before applying the grease gun will prevent injecting the dirt and debris into the bearing.
Apply the grease gun to the grease fitting and pump the grease into the bearing slowly. Observe the grease relief port for signs of old grease discharging from the port. When grease is observed relieving from the port, stop greasing.
Run the electric motor for half an hour with the relief plug removed from the motor. As the grease distributes and works through the bearings, the open port allows for any excess to vent.
Shut the motor off and replace the relief port.
Place a small dab of grease onto the grease fitting to help protect it from dirt and corrosion until the motor is due for re-lubrication.