As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER DEPARTING, HOSPITAL CREW NOTICED RUBBER SMELL IN CABIN, PILOT CARRIED OUT A PRECAUTIONARY LANDING . AFTER SHUTDOWN, THE HOT RUBBER SMELL WAS DETERMINED TO BE COMING FROM THE AIR CONDITIONING COMPRESSOR BELT. THE CLUTCH WAS DETERMINED TO BE SLIPPING. AC SYS WAS DEFERRED TO MEL AND PARTS PLACED ON ORDER.