As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - FLT 4216 - THE CREW REPORTED RELAYS CLICKING AND A BURNING ODOR IN THE COCKPIT. MAINTENANCE DETERMINED THE SOURCE OF THE BURNING ODOR TO BE COMING FROM THE NR 1 AIRCONDITIONING PACK. THE NR 1 AIRCONDITIONING PACK WAS PLACED ON MEL REFERENCE 21-51-00, CATEGORY ''C'' CONTROL NR 003258. THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. (M)