As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED UPON ENTERING ICING CONDITIONS THE COCKPIT FILLED WITH SMOKE AND ACFT PERFORMED AIR RETURN BACK TO EWR. MX INSPECTED AND RAN A/C SYSTEMS NOTED NR 1 PACK ACM SEIZED. REMOVED AND REPLACED NR 1 ACM AND HEAT EXCHANGER WITH OPERATIONAL CHECKS GOOD. A/C WAS APPROVED FOR RETURN TO SERVICE.