What was found
DFW - FLT 1938 - DFW-CLE, ON CLIMB-OUT, TAIL COMPARTMENT HIGH LIGHT ILLUMINATED. FOLLOWED CHECKLIST AND LIGHT EXTINGUISHED WHEN LEFT PACK WAS TURNED OFF. LIGHT ILLUMINATED AGAIN WHEN POWER ADVANCED TOWARD CLIMB POWER. RETARDED POWER AND LIGHT EXTINGUISHED. RETURNED TO DFW AND LANDED WITHOUT INCIDENT. REPLACED LEFT PACK HEAT EXCHANGER EXHAUST SLIP DUCT SEAL. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)