Tip: In a new motor with new brushes the back of the brush will be flush with the brush housing, as the brush wears the distance into the housing will increase. (See top view drawing below.) A quick measurement of the depth will be sufficient. When the brush is 5/8” into the holder it will need replacement. If in doubt change the brushes. Carry spares.
When changing brushes, be sure the phillips screw holding the brush wire and power lead is tightened properly to assure a good electrical connection.
Commutator wear can be measured by installing new brushes and measuring the depth in the housing. A properly maintained motor will show little wear here (brush end flush with the housing). A worn commutator may need to be resurfaced to prevent excessive and rapid wear of replacement brushes.
March Water Pump
The water pump motor brushes are 7/16” when new. Replace them before the spring becomes close enough to damage the commutator.
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