What was found
INTERMITTENT APU FIRE WARNING AFTER TAKE-OFF FROM KSUS. CREW SHUT DOWN APU AND ACTIVATED APU COMPARTMENT FIRE EXTINGUISHER. RETURNED TO KSUS. MAINTENANCE AT KSUS INSPECTED APU AND COMPARTMENT FOR HEAT OR FIRE DAMAGE, NO DEFECTS NOTED. DEFERRED APU SYSTEM IN ACCORDANCE WITH THE FAA APPROVED MEL. CONTINUED WITH MISSION WITH NO OTHER WARNINGS. SUSPECT APU COMPARTMENT TEMPERATURE HIGH DUE TO APU OPERATED FOR ALMOST AN HOUR BEFORE DEPARTURE AND WEATHER CONDITIONS IN KSUS WERE IN THE MID 90 DEGREES. NO DEFECTS OR REASON FOUND FOR FALSE WARNING OTHER THAN AIR TEMPERATURE AT THE TIME.