Thread: Sick 240V pistol drill diagnosis?

Originally Posted by BaronJ

Hi Guys,

The usual failure of this type is one of three things:
Motor brushes,
Commutator segment,
Debris in and around the armature,
Sometimes it results in winding burn out, but that is usually quite obvious from the appearance and smell.

Is the gap between commutator segments clean ?

When I get another chance I'll disassemble again and do the suggestions.
It'll wait until I have time and inclination.

You may need a Megger to test an armature properly.
Measure resistance between adjacent segments with a DVM ( R all the same ) AND wrap some copper wire around the commutator and Megger between the Comm and the shaft. ( infinity, if low you have a short to earth. )

I don't have a Megger, but good to know the method, thanks.