On Jan 26, 8:44 pm, wrote:
I noticed that our central vac didn't sound right today. I took the plastic
housing off the top of the motor so the commutator and brushes were visible
and started it up. After a few seconds of operation I start to see the blue
spark between the brushes and commutator start to extend almost 1/2" in the
direction of rotation around the commutator. As this happens the speed of
the motor slowly begins to drop. The motor was overhauled last April; new
bearings and brushes.The vacuum is 22 yrs old so the commutator on the motor
has seen a lot of wear but it looks in reasonable shape. Anybody have an
idea what might be happening here?

Adding to Eric's commen\ts, the overhaul should also have included
truing and smoothing the commutator. My bet is on wrong brush type for
the unit. Central vacs are robust machines that can draw considerable
current and require a high conductivity brush and maximum commutator
contact. The proper brush may even need considerable copper content
like those in auto starter motors. A set of OEM brushes might help the
problem. HTH

Joe