Have a Carrier 58RAV hvac. Blower motor does NOT come on. It makes a humming sound. After ruling out the capacitor and other components, removed the motor and capacitor, reconnected them YESTERDAY, ran power directly to the motor with capacitor in place. Bingo, it worked fine. Reinstalled, ran the system for a few hours, then back to square one. Waited overnite, disconnected all wires going to the motor from the control circuit board, reset the breaker, etc. ran power directly to the motor with same then with a new capacitor. In all cases, the motor just makes a humming sound. Bad motor? IF so, why work 11 yrs, then not for several hours, then work again for a few hours, and fail again.
- No codes, ruled out transformer (115v going in, 26v out to the board), motor calls for 7.5uf cap. I tried with a 7.0uF -+10% Same results.

Sounds like you have a start winding opening up when it gets hot. Motors can do strange things at times. You need to replace it. Make sure to oil new motor when you put it in with high speed oil. Match capacitor to new motor, also, and get rotation correct. DrTom4444