As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENROUTE FROM PHL TO ACK, NOTICED A BURNING ELECTRICAL ODOR FOLLOWED BY THE EMERGENCY PRESSURIZATION LIGHT. ACCOMPLISHED AIR TURN BACK TO PHL CLEANED LINTS AND DEBRIS FROM 3RD HEAT EXCHANGER COOLING FINS, RAN AIRCRAFT WITH NO ABNORMAL INDICATIONS FROM THE AIR-CONDITIONING SYSTEM (HOT AND COLD, NORMAL AND MANUAL). ALL WORK PERFORMED IAW CE560 MM CHAPTER 21-11-00, 21-31-04 AND 21-51-00.