As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIGTAILS 52 AND 53 ODOR OF BURNING RUBBER WHEN HOOKED UP. PIGTAIL 52 HAS ACRID ODOR AT CONNECTOR. CONNECTOR TAPED OFF. C-B PULLED AND COLLARED. PIGTAIL 53 UNABLE TO FAULT. CATERING AND CREW ADVISED. REPLACED PIGTAIL CABLE AT 52 AND 53.