1
Locked rotor / seized airend
CheckBar over by hand (lockout/tagout first). Should rotate freely.
FixIf seized, airend rebuild required.
2
Single-phasing (3Φ)
CheckMeasure all three legs at motor; check phase loss relay.
FixRestore lost phase; check fuses, contactor tips, terminations.
3
Low supply voltage
CheckVoltage at motor terminals under load — must be within ±10% nameplate.
FixCorrect supply; check wire size and length (voltage drop).
4
Wrong overload setting
CheckOL set to 115–125% of motor FLA on nameplate.
FixReset dial / select correct heater.
5
Discharge pressure above setpoint
CheckVerify pressure switch / load setpoint; verify unloader function.
FixAdjust setpoint; repair unloader.
6
Motor winding short / ground fault
CheckMegger windings to ground (>1 MΩ minimum).
FixRewind or replace motor.
Safety
Lockout/tagout before opening enclosures. Verify zero energy. Bleed system pressure before opening any pneumatic connection.