As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT CRUISE ALTITUDE THE CREW MEMBER VERY BRIEFLY SMELLED A HOT RUBBER SMELL WITH THE AIRCRAFT AIR CONDITIONER BECOMING INOPERATIVE SIMULTANEOUSLY. THE SYSTEM WAS TROUBLESHOT AND FOUND THAT THE AIR CONDITIONING COMPRESSOR DRIVE PULLEY WAS DEFECTIVE CAUSING THE DRIVE BELT TO GET HOT ON THE PULLEY CAUSING THE HOT RUBBER SMELL.