I have a Hoover upright vacuum cleaner model U3350. When switched on, the motor makes a humming sound, and it smokes after the time it takes to turn it on and off to see if it's working!
I took the motor out thinking the brushes may need replacing, but they looked fine - well over a centimeter left. I made sure they were free to move in their guides and the spring mechanism is pushing them down the guides OK.
As the brushes themselves looked fine I cleaned up the area on the motor shaft where the brushes contact (I think this may be called the commutator) as it looked black. I lightly sanded back to the original copper colour and cleaned out the grooves between the sections of the commutator.
On reassembly, the motor still didn't work and it smoked again.
So, I took the motor back out. The commutator is again black with heavy deposits from the brushes.
Can anyone tell me from this description where the problem lies please. Is this a sign of a burned out motor, or does the problem lie elsewhere?
I appreciate any help.