What was found
DFW - FLT 407 - AFTER TAKEOFF FROM DFW EN ROUTE TO PHX, TAIL COMPARTMENT HIGH TEMPERATURE LIGHT ILLUMINATED AT 9,000 FEET. AIRCRAFT RETURNED TO DFW AND LANDED WITHOUT INCIDENT. RESECURED SEAL BETWEEN AIR CONDITIONING PLENUM AND HEAT EXCHANGER ON LEFT HAND OUTBOARD SIDE OF TAIL COMPARTMENT. SYSTEM GROUND CHECKED, NORMAL OPERATION.