Originally published April 2008

What’s That Smell?

When internal trimmer components get wet.

A periodic complaint we get on older model trimmers is that the motor is running hot and giving off an unfamiliar odor. Many customers assume that this is a motor bearing problem. Wehmer model trimmers are built with non-replaceable sealed bearings which seldom provide maintenance problems. 30 years of motor life is not atypical. Both 1/2 and 3/4 HP motors are built with superior moisture protection as far as the bearings go. The motor itself, however, is not water proof, and water that flows into the windings and armature of the motor can cause permanent damage. For water to get that far into the trimmer, it must also get to the drive belts for the fine wheel and the fine wheel shaft and bearing.

Water that gets into the motor, belts, and shaft and bearing is a result of insufficient drainage. It’s a simple matter of water coming in being greater than water draining out. Once the belts are wet, they begin to slip. Trimming with the fine wheel when drive belts are damp or moist will result in a “burnt rubber” smell. The bearing that supports the fine wheel shaft is also “moisture resistant” but not water proof. Extended exposure to water with a plaster mixture will cause the bearing to rust and eventually fail. As oxidation and plaster residue builds up in the bearing, it causes the bearing to bind. This binding results in motor overheating as the motor works increasingly harder to drive the fine wheel. Wehmer trimmer motors are thermally protected to avoid permanent damage. If your trimmer just mysteriously stops, it could be the thermal switch. Turn the power switch off and wait twenty minutes for the motor to cool. Newer machines are equipped with a red thermal reset switch on the back of the motor. If your trimmer has one, push it in until it clicks and start your machine. If there is no red button, you have an auto-reset thermal switch. Simply repower the machine after it has cooled.

Belts and shaft-and-bearing assembly can be field serviced. Wehmer can provide parts and complete instructions.

Important Note: Any motor used in a wet environment must be connected to a grounded outlet with GFI (Ground Fault Interruption) protection. Always unplug your machine when performing troubleshooting activities that require removal of the front cover.