What was found
MFR FLIGHT 2851: AFTER NORMAL START WITH NR 2 ENGINE FIRST WHEN FLAPS WERE SELECTED TO 15 DEGREES, THE FLAP POWER CAUTION LIGHT ILLUMINATED. FOLLOWED CHECKLIST AND RESET FLAP CONT CB. THE CAUTION LIGHT WENT OUT AND FLAPS OPERATED NORMALLY. MAINTENANCE REPLACED THE FCU IAW AMM TASKS 27-52-01-000-801 AND 27-51-01-400-801. NO HELP. THEN REPLACED FLAP POWER UNIT IAW AMM TASKS 27-52-000-801 AND 27-52-01-400-801. FUNCTIONAL CHECK GOOD. NO FAULTS NOTED. NO LEAKS NOTED. FLAP POWER CAUTION LIGHT DID NOT ILLUMINATED DURING TESTS. AIRCRAFT RETURNED TO SERVICE.