[Al Skierkiewicz]

The FP motors have a few failure signs, some of those are mentioned above. It is possible when the motor is in stall to only burn one winding. This will give you some false indications in that the motor smells bad but still seems to function. The FP motors have three windings, so one burning reduces the output power by almost a third but since the winding is invariably shorted, the current consumption skyrockets and the heat goes up. You will ask "how you will know if you smell a bad motor?" A burned motor leaves no doubt, it is vastly different than the mechanical, hot oil and brush, smell the motor normally has. A simple visual inspection with a flashlight will show one or more of the following...
1. Loose or cracked fan.
2. A discolored winding compared to the others.
3. Discoloration of the commutator (the copper contacts on the armature)
4. Smoke damage
5. Completely burned commutator and windings.
Arcing is not a sign that the motor is defective, all DC motors will arc at the brushes as part of their operation.