CORP ACFT HAS UNSAFE LIGHT WHEN GEAR EXTENDED.

Narrative

PROBLEM AROSE WHEN GEAR SELECTOR PLACED IN DOWN POS TO COMMENCE ILS 28 APCH. L MAIN GEAR SHOWED AS UNSAFE. PAX WHO HAS EXPERIENCE WAS SENT BACK TO VISUALLY INSPECT. GEAR APPEARED TO BE DOWN. LIGHT BULB CHKED OKAY. HYDRAULIC PUMP CHKED OKAY. REVIEWED EMER CHKLIST. NO FURTHER ACTION INDICATED. CYCLED GEAR WITH NO RESULTS. DECIDED L MAIN GEAR WAS DOWN; BUT NOT LOCKED. ADVISED ATC AT ONSET OF PROBLEM. REQUESTED VECTORS OFF THE ILS WHILE REVIEWING SITUATION. UPON EVALUATION; REQUESTED THE ILS 28 APCH AND FIRE AND RESCUE EQUIP. ATTEMPTED TO LOCK GEAR WITH SIDE LOAD UPON CONTACTING RWY WITH NO IMPROVEMENT. THEN SLOWED ACFT AND MADE NORMAL LNDG. EVACUATED ACFT AND SECURED ON RWY. NO DAMAGE OR INJURY. UPON VISUAL INSPECTION; I DETERMINED THAT OVER CTR LOCK WAS NOT ENGAGED. PHYSICALLY PUSHED LOCK IN PLACE. REBOARDED ACFT AND TAXIED TO RAMP. GEAR LIGHTS CAME ON UPON STARTUP AND HYD RETURNED TO SAFETY MODE. PROBLEM TRACED TO BINDING OF LOCK CAUSED BY WEAK SPRING AND MIN CLRNC IN HOUSING. CLRNC CORRECTED BY USING SMALLER THICKNESS SPACING WASHERS. NEW SPRING INSTALLED. ATC HELPFUL BY NOT CONSTANTLY ASKING FOR INFO AND UPDATES. THIS ALLOWED ME TO EVALUATE PROBLEM WITHOUT INTERRUPTION. ESPECIALLY IMPORTANT IN SIMPLE PLT OPS. ATC WAS OBJECTIVE AND PROFESSIONAL; THUS MAINTAINING NORMAL 'FEELING' IN COCKPIT; WHICH HELPED KEEP ANXIETY LEVELS DOWN AMONG PAX AND CREW.