My sister has a Heil Comfortmaker 10. If the furnace has been off for awhile the blower motor works fine, but sometimes when the furnane kicks on the motor will only hum and when not blow even turned to on. I spinned the wheel but it still won't start. It will just set there and hum. The motor has a capacitor hooked to it. Would it be the motor since turning it will not make it start or can the capacitor be bad? I don't think it is the relay becauses the motor hums. Any help would be greatly appreciated since she is on a very limited budget.

Normally if you spin the motor and it starts then it's the capacitor. If it doesn't start then it's the motor.
Most motors have 3 speeds. Make sure the motor is only getting power at ONE speed at a time.
Also make sure the motor spins freely and is not stiff when you turn it.

Does the motor spin freely, even when power is supplied to it? The bearings may have gone bad causing the rotor and stator to touch each other. Only when the magnetic field is generated will the stator pull the rotor into it.