As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT THE FLIGHT CREW GOT AN INDICATION THAT THE NR 1 PAC OVERLOAD AND IN MANUAL THE SYSTEM WENT TO OVERHEAT. AIRCRAFT RETURNED TO PIT. MAINTENANCE INSPECTED AND FOUND THE OVERTEMP SWITCH BAD. THE NR 1 PACK WAS DEFERRED PER MEL 21-51-00-1-1.