As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THRU 37000 FT, NOTICED A SUDDEN SMELL OF BURNING RUBBER. F/A''S REPORTED THAT IT SOUNDED LIKE THE A/C AIR WENT OFF IN THE CABIN. R DUCT PRESSURE DROPPED TO APPROX 25 PSI, EVENTUALLY RETURNED TO NORMAL AND SMELL DISSIPATED. SMELL WAS CONFINED TO COCKPIT. F/A''S IN FWD GALLEY DID NOT SMELL IT UNTIL COCKPIT DOOR WAS OPENED. REPLACED LEFT ACM AND LOW LIMIT VALVE PER MM.