- the condition and degree of wear of the brushes. The brushes must move freely in the grooves of the brush holders.
- contact of the brushes with the collector and the pressure of the springs on the brushes;
- collector appearance. The collector can only be cleaned with a clean rag soaked in gasoline or trichlorethylene. Grind the collector only with fine-grained sandpaper. It is forbidden to use emery cloth for this purpose;
- the condition of the self-lubricating bushings of the covers. Before installing new bushings, soak them for at least 20 minutes in engine oil (SAE 30/40);
- appearance of the armature and stator. Make sure that their windings do not have any breaks or burn marks.