What was found
INFLIGHT DISPLAY COOL MASTER CAUTION MESSAGE. RAN QRH, MESSAGE WOULD NOT EXTINGUISH. ACFT RETURNED, EMERGENCY DECLARED, R & R NR 2 DISPLAY COOL FAN IAW AMM 21-24-19. IPC 21-24-00, FIG 10, ITEM 38 AND R & R COCK DISPLAY COOL AIR FILTER IAW 21-24-15. OPS CK GOOD, NO FURTHER DEFECT NOTED.