What was found
DURING PRE-TAKEOFF CHECKS, LT HAND PRESSURIZATION WENT INTO EMERGENCY PRESSURIZATION MODE AND WOULD NOT RESET TO NORMAL. PILOT RETURNED TO DEPARTURE AREA AND ABORTED TRIP. TROUBLESHOT TO FAILED RELAY IN MODULATING VALVE CONTROL BOX. FAILED RELAY INTERRUPTED GROUND PATH FOR EMERGENCY PRESSSURIZATION VALVE CONTROL BOX. FAILED RELAY INTERRUPTED GROUND PATH FOR EMERGENCY PRESSURIZATION VALVE CAUSING IT TO OPEN. REPLACED MOD. VALVE CONTROL BOX WITH SERVICEABLE UNIT. OPERATIONS CHECKED GOOD.