What was found
ON PRE-FLIGHT DEPARTURE RUN-UP AND OPERATIONAL CHECK, DISCOVERED LEFT PROPELLER PITCH LIGHT INOPERATIVE. REPLACED PROXIMITY SWITCH, CORRECTED THE DEFECT. SUBMITTER STATED THIS IS THE THIRD LOW PITCH STOP PROXIMITY SWITCH FAILURE IN 413 HOURS, AIRFRAME TIME SINCE NEW. SUBMITTER SUSPECTS DEFECTIVE SWITCH, OR SWITCH WILL NOT TOLERATE THE ENVIRONMENT.