Brushed DC motors with armature, commutator and drive shaft are very often used in the automotive environment. One of the failure mechanisms of these DC motors is the so-called pasting. This paste on the commutator of the DC motors consists of the residue of carbon brushes mixed with various lubricants from e.g., oil on the ball bearings on the drive shaft. This lubricants seep through the motor shaft bushing to the commutator, mix with the carbon residue from the brushes as the motor runs and accumulate between the copper segments in the insulation grooves of the commutator until a thick layer of this conductive oily carbon paste shorts the commutator segments together. This causes the DC-Motor to draw surplus current, what causes the overheating of the armature and leads to the failure of electric motor.

Test methods such as current measurements with an oscilloscope and optical microscopy are used for the analysis of pasted DC Motors. The aim of this research is to identify and to understand the mutual dependencies between composition of the lubricants used for mechanical components in the immediate vicinity of the motor, constructive-geometric design of the motor itself, varying load cycles of motor, as well as the selection of carbon brush material. Interpretation of the obtained results for the improvement of the quality of vehicles provides a central point of this research.