What was found
(CAN) THE RT ENGINE RPM WENT TO ZERO IN CLIMB. AIRCRAFT RETURNED TO BLOCKS. THE GAUGES WERE SWAPPED BY THE FLIGHT CREW AND THE FAULT FOLLOWED THE GAUGE SO THE GAUGE WAS REPLACED AND ACFT RUN AND CHECKED SERVICIBLE. ACFT RELEASED TO SERVICE. 30 MINUTES INTO FLIGHT THE NEWLY INSTALLED GAUGE STATED TO READ INCORRECTLY. ACFT RETURNED TO BASE AND WIRING WAS FOUND AT FAULT AND CORRECTED. ACFT RETURNED TO SERVICE.