A lot of times a manufacture will change a vendor that supplies a specific part for a tool. It could be as simple as a screw or a spring. Since they are getting the part from a different vendor they will change the part number and sometimes put a different type number on that tool, even if that new part number will fit either types. In your case I think that bases are the same just different vendors supplying the same parts.

Hope that makes sense,

WJA

Hi jimshannon,

I would start by checking the brushes. Sometimes when a brush is worn down to almost nothing it will arch a bit. If the brushes still have lots of usable length left then the problem will be with the armature. When the armature shorts out it produces lots of sparks and arching. If the armature is bad then will will also want to look over the field. Many times the field will either be damaged by the bad armature or will be the cause that the armature went bad.

The brushes are part #869659
The armature is part #903660
The field is part #903659

I hope this helps with your repair!

-UtahAV
-Mark