If the bearings in an AC motor are overheating, it may be due to several reasons:

1. Insufficient lubrication: The bearings may not be receiving adequate lubrication, causing excessive friction and heat buildup.

2. Contaminants: The bearings may have been contaminated with dirt or other foreign substances, causing them to overheat.

3. Overloading: The motor may be overloaded due to excessive load or a mismatch between the motor and the load, causing the bearings to overheat.

4. Misalignment: The motor shaft may be misaligned, causing the bearings to operate at an angle and wear out faster.

5. Electrical issues: The motor may have electrical issues such as damaged windings or a faulty starter, causing it to operate at an incorrect frequency and overheat the bearings.