What was found
MZT - DIVERSION - FLT 0671 - EN ROUTE FROM PVR TO PHX AT CRUISE, WHEEL WELL FIRE WARNING LIGHT ILLUMINATED AND FIRE BELL SOUNDED. DIVERTED TO MZT AND LANDED WITHOUT FURTHER EVENT, FIRE WARNING LIGHT EXTINGUISHED AFTER 20 MINUTES WHEN LANDING GEAR WAS LOWERED. FLIGHT CREW PERFORMED VISUAL INSPECTION OF WHEEL WELLS AND FOUND NO EVIDENCE OF FIRE OR ANY OTHER DEFECT. MAINTENANCE WAS FLOWN DOWN TO MZT AND REPLACED THE OVERHEAT COMPARTMENT ACCESSORY UNIT M237 IAW BMM 26-17-00. VENDOR BENCH TEST OF COMPARTMENT OVERHEAT ACCESSORY UNIT WAS NO FAULT FOUND, UNIT FUNCTIONAL TESTED GOOD, TEST WAS CONDUCTED SEVERAL TIMES WITH NO DEFECTS, CLEANED CIRCUIT CARD AND WIRING, UNIT RETURNED TO SERVICE.