What was found
IN CRUISE AT FL250 #1 RUD HYD CAUTION ILLUMINATED AND STAYED ON ENTIRE FLIGHT. AFTER A FEW MINUTES RUD CTRL ILLUMINATED AND STAYED ON FOR A MINUTE OR TWO, THEN DISAPPEARED. RUD CTRL MESSAGE RETURNED TWO MORE TIMES IN FLIGHT BUT DISAPPEARED EACH TIME. AIRCRAFT FLEW NORMALLY AND AIRSPEED WAS RESTRICTED TO 200 KIAS PER E/A CHECKLIST. HYD PRESSURES AND QUANTITIES BOTH NORMAL. LANDING UNEVENTFUL. REMOVED FROM SERVICE. REPLACED #1 HYD SYSTEM RUDDER PCU. OP CHECKS GOOD. THESE CAUTION LIGHTS DID NOT RETURN. RETURNED TO SERVICE.