What was found
YIP - FLT 19041 - JEWEL LIGHT CAME ON WHILE CLIMBING THROUGH 1,000 FEET. AI RCRAFT RETURNED TO POINT OF DEPARTURE AT YIP AND MADE AN UNSCHEDULED LANDING. NO EMERGENCY PROCEDURES WERE NECESSARY. CORRECTIVE ACTION: THE HYDRAULIC RESERVOIR PRESSURIZATION SYSTEM NON-RETURN VALVE WAS FOUND STUCK IN THE CLOSED POSITION. THE VALVE WAS REPLACED WITH A SERVICEABLE PART. PERFORMED A GROUND RUN OF ENGINE TO PRESSURIZE THE SYSTEM AND NO DEFECTS WERE NOTED. (X)