What was found
(CAN) DURING CLIMB OUT OF ZWH, PILOT NOTICED A SIGNIFICANT DROP IN AIRSPEED WITH THEALTIMETER & VSI ACTING ERRATICCALLY. THE ALTERNATE PITOT STATIC SOURCE WAS SELECTED & AIRSPEED VSI & ALTIMETER RETURNED TO NORMAL. PRESSURIZATION DIFFERENTIAL INDICATOR STAYED AT ZERO EVEN THOUGH THE CABIN WAS PRESSURIZING. MAINTENANCE FOUND THE REFERENCE LINE BETWEEN THE L/H AIRSPEED STATIC SOURCE AND THE CONTROLLER SPLIT. THE LINE WAS REPLACED AND THE PITOT STATIC SYSTEM TESTED FOR LEAKS. THE AIRCRAFT RETURNED TO SERVICE.