What was found
FLT 3158 - THE FLAP FAILED TO EXTEND WHILE APPROACHING. EXTENDED THE FLAP BY STANDBY MODE. ON THE GROUND, EXTENDED AND RETRACTED THE FLAP BY NORMAL MODE AND OKAY, BUT 'ELEVATOR DISAGREE' MESSAGE APPEARED. THE FLIGHT WAS DELAYED. CHECK FOUND FSEU SHOWED NO FAULT CODE AND STABILIZER TRIM AND DISAGREE ASSEMBLIES WERE OKAY. SENT A MECHANIC TO CHECK AND HE FOUND NO PROBLEM. REPLACED FSEU NR 1 ASSY WITH PN 285N001-40 TO DETECT FAULT.