What was found
THE CREW RECEIVED A DISPLAY COOL FAN FAIL CAUTION MESSAGE FOR ALL OF THE DISPLAYS. THEY RAN THEIR QRH AND RETURNED TO THE FIELD. ATC DECLARED AN EMERGENCY FOR THE CREW AND THEY LANDED WITH OUT INCIDENT AND TAXIED TO THE GATE. THE AIRCRAFT CURRENTLY HAS A DISPLAY COOL FAN NUMBER 2 ON MEL. MAINTENANCE REPLACED THE DISPLAY FILTER AND COMPLIED WITH THE OPS CHECKS OF THE NUMBER 1 DISPLAY FAN AND EVERYTHING OPS CHECKED GOOD WITH NO FURTHER PROBLEMS.