What was found
DURING CLIMB OPERATION THE FO'S CDI NEEDLE DID NOT DEVIATE WITH COURSE CHANGES WITH THE VOR SELECTED. ALSO, THE CAPTAINS CDI WAS UNREADABLE ON LOCALIZER, SHOWED FROZEN, CENTERED THEN RAPIDLY MOVED LT OF COURSE. THE ACFT RETURNED TO DEPARTURE WHERE IT LANDED WITHOUT INCIDENT. POST FLIGHT INSPECTION WAS PERFORMED, R & R THE NR 2 NAV /GPS SWITCHING RELAY. PERFORMED OPS CHECK OF GPS INTERFACE AND VOR/ILS NAV A/T. NO DEFECTS WERE NOTED. ACFT WAS RETURNED TO SERVICE.