I had my DC25 repaired recently, because the brush did not work anymore. I tried several time to reset the brush bar motor, no way. Furthermore, the way the fault happened, spark close to the motor and trip of the magneto-thermal protection of my home, made me think to a short circuit, so I shipped the whole vacuum cleaner for repair.
I never knew the failure cause, but it happened again that cleaning a carpet my home protection tripped, with a big spark in proximity of the brush bar motor. I thought of the same failure as before, but strangely the brush bar still worked. I also observed that at the moment of the protection trip, the washing machine was on, as well as a lot of other household appliances.
So I have this theory. The DC25 with brush bar on made trip the protection for overload in both cases, probably due to fact that a lot of other devices where on. The spark was not caused by short circuits, but by the overvoltage created in the DC motor commutator, due to the sudden current break in the motor coil. If it is like this, last time it was the rectifier to be damaged by the overvoltage. Someone knows if there is any flyback diode across the brush bar motor? Thank you.