I've never known carbons to do this before!

[Discountdysons]

Maybe one of the mvacs techs have done it successfully?

We never change carbon brushes any more. They always seem to spark like a firework afterwards and/or have a very short life. The armature is usually shot.

We only sell them because people kept badgering us for them.

Faster and more reliable to change the motor.

We are the same. Always end up the motor blowing again

[beko1987]

Ah shame that.

I know a man who is trying, and will report back with his findings.

On a slightly related note, I have 2 Hoover Compact motors from the mid 80's that spark like a bastard since I removed the brushes for checking. I;ve bought a set of comm sticks to see if it works. If it does, then I might try and clean up a DC motor once I work it out on a slow pottery 700w motor first!

[MikeR]

Generally, the windings on the armature fail. If you give the comm a quick clean and measure the armature coils you will find some will vary greatly.

Keith

[tnix99]

I've successfully soldered new carbons on but they sparked really badly when I ran the motor.  Can someone tell me why some motors spark when switched on? Is it just dirt on the armature?