Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!). Check the isolation of the motor windings.
[pdf] Fill the oil reservoir with proper oil (Air Tool oil or 10W grade equivalent for 9 lb.and 15 lb.class and Rock Drill oil for the 38 lb.and 60 lb.class.) Check all nuts and bolts to ensure they are tight on the tool. Make sure retainer locks in place. Replace retainer and or springs if worn.
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