As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PACK OFF & PACK TEMP LIGHTS ILLUMINATED FOLLOWED BY BLEED OFF LIGHT. PRIOR TO PACK TRIP, THE PNEUMATIC SYS COULD BE HEARD CYCLING. FLIGHT RETURNED & LANDED WITHOUT INCIDENT. ACFT REMOVED FROM SERVICE. REPLACED LT PACK REHEATER & CONDENSER MPN 1942765. SYS GND CHECKED NORMAL OPERATION CLOSED.