What was found
AT FL 360 RECEIVED AFT AVIONICS COMPARTMENT SMOKE WARNING WITH A RED LIGHT SMOKE INDICATION WITH A HORN ON THE OVERHEAD PANEL; THIS HAD NO ASSOCIATED ECAM. SILENCED THE ALARM, AND QRH PROCEDURE CATRRIED OUT. AFTER COMPLETION OF QRH PROCEDURE THE RED LIGHT REMAINED AND THE HORN SOUNDED A SECOND TIME. CAPTAIN DECLARED EMERGENCY AND MADE A UNEVENTFUL UNSCHEDULED LANDING AT OKC. VISUAL INSPECTION OF AFT AVIONICS RACK REVEALED NO DEFECT. REMOVED AND REPLACED AFT AVIONICS RACK COOLING FAN ASSY, OPERATION CHECK NORMAL PER LTV AMM 23-39-00.