Section 5.Troubleshooting

DC Electric Motor

Short-Circuited Winding

A short-circuited winding is one where the insulation on the field or armature has broken down at two or more points. The breakdown creates a low resistance path, permitting current to flow from one turn of the coil to another adjacent coil turn, without actually flowing through the coil wire. The result is a decrease in total resistance of the motor winding and an increase in the current flow. The severity of the short circuit depends on its location.

A shorted motor may be indicated by:

•Slow or sluggish operation

•Running faster than normal

•Overheating

•Blowing a power fuse

•Severe burning or discoloration on one or two commutator segments every 90° of rotation

These symptoms can also be caused by problems other than the motor itself, such as:

•Brake too tight or dragging

•Wheel bearings too tight

•Faulty transmission

•Binding in an attached pump

Testing a motor for shor t-circuited windings requires special equipment at a motor rebuilding facility.

Model 6210 Maintenance Manual

Publication: 1146947, Revised: 12 Jan 2017