Motor terminal connections are incorrect. Motor shaft is locked by a bad bearing. Impeller is locked by debris. Wiring to pump is undersized. Power company supply voltage is low.
Ventilation is inadequate for motor.
Choosing the right Automatic pool cleaner Determining the correct pool cleaner isn't too hard. Many of the older pool sweeps like the Arneson Pool Sweep and the Polaris 180 use a separate booster pump. Provided the booster pump is still in good working order you can use it with any of the new pressure style pool sweeps, saving yourself a lot of money. Examples of suction cleaners are the Kreepy Krauly, and Baracuda pool cleaners. Since these cleaners work off the vacuum of the pools filtration system, a separate booster pump is not needed.