A B737-300 FLC DIVERTS BECAUSE OF AN INDICATION OF A WHEELWELL FIRE WARNING; ONLY TO FIND THAT IT WAS A FALSE WARNING AFTER LNDG AT MMMZ; FO.

Narrative

THE FLT HAD BEEN AT CRUISE ONLY A COUPLE OF MINS WHEN THE FIRE WARNING BELL SOUNDED AND THE 'WHEELWELL FIRE' WARNING LIGHT ILLUMINATED. WE ACCOMPLISHED THE QRC AND QRH PROCS; EXTENDED THE LNDG GEAR AFTER SLOWING THE ACFT; BUT THE FIRE WARNING LIGHT REMAINED ILLUMINATED. WE STARTED TO DSND TO A LOWER ALT; DECLARED AN EMER WITH MAZATLAN CTR; AND COORDINATED OUR DIVERSION WITH MAINT CTL AND COMPANY DISPATCH. MAZATLAN WAS THE CLOSEST SUITABLE ARPT 'IN POINT OF TIME.' WE COORDINATED A LOW ALT 'FLY-BY' OVER THE TWR; WHO RPTED THAT OUR LNDG GEAR APPEARED TO BE NORMAL AND UNDAMAGED. THE 'WHEELWELL FIRE' WARNING LIGHT FINALLY EXTINGUISHED AS WE APCHED MAZATLAN ARPT (APPROX 20 MINS AFTER ILLUMINATING). I BRIEFED THE FLT ATTENDANTS THAT WE WERE MAKING A 'PRECAUTIONARY LNDG;' AND A NORMAL FLAPS 40 DEG LNDG WAS ACCOMPLISHED ON RWY 26 WITHOUT INCIDENT. WE HAD REQUESTED THAT THE TWR HAVE EMER VEHICLES STANDING BY; BUT THEY WERE NOT THERE. A NORMAL TAXI TO THE GATE WAS ACCOMPLISHED. POSTFLT INSPECTION REVEALED NO APPARENT DAMAGE OR APPARENT CAUSE FOR THE FIRE INDICATION.