Cell case current leakage.
External power fails to energize aircraft.
Battery switch in OFF position.
Keylock switch off.
Battery power too low.
Defective or incorrectly polarized external power source.
Defective external power receptacle.
Defective external power relay.
Defective external power overvoltage monitor.
Loose or wrong connection in external power circuit.
Landing gear will not retract or extend.
Circuit breaker tripped in control or motor circuit.
Loose motor ground connection.
Defective control switch.
Landing gear will extend but will not retract.
Open circuit between landing gear switch and control relay.
Up solenoid of control relay inoperative.
Open circuit between control relay and up winding in motor.
Defective up limit switch.
Landing gear will retract but will not extend.
Down limit switch inoperative.
Open circuit between control relay and down winding of motor.