As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW MADE AN UNSCHEDULED LANDING DUE TO A STRONG ELECTRICAL SMELL THROUGHOUT THE AIRCRAFT CABIN ON CLIMB-OUT. MAINTENANCE INSPECTED AIRCRAFT AND FOUND THAT ALL AIRCRAFT BAY HEAT EXCHANGERS WERE REPLACED THE NIGHT BEFORE DURING SCHEDULED OVERNIGHT MAINTENANCE, WITHOUT SUFFICIENT RUN TIME. CABIN FILTERS WERE REMOVED AND REPLACED IN ACCORDANCE WITH ATSM 21-00-00810-802 AND SIL 21-132. APU BLEED AND ENGINE BLEED SYSTEMS RAN UNTIL SMELL DECREASED IN ACCORDANCE WITH AMM 21-21-41-PB401.