As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LAX - INFLIGHT PSP-ORD CREW REPORTED TAIL COMPARTMENT TEMPERATURE HIGH LIGHT ILLUMINATED AFTER TAKEOFF. EMERGENCY DECLARED FLIGHT LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. FOUND RIGHT PRIMARY HEAT EXCHANGER CRACKED. REPLACED PRIMARY AND SECONDARY HEAT EXCHANGER FOR RIGHT PACK. SYSTEM GROUND CHECK NORMAL OPERATION.