What was found
WHILE IN CRUISE FLIGHT, RETURNING TO BASE (WITH NO PATIENT ON BOARD) THE MED CREW REPORTED A SMELL OF BURNING RUBBER COMING OUT OF THE AIR CONDITIONING VENTS. PILOT PERFORMED A PRECAUTIONARY LANDING WITHOUT INCIDENT IN A FIELD. MAINT INSPECTED THE A/C SYSTEM AND FOUND NO EVIDENCE OF A/C SYS FAILURE. SUSPECTED INTERNAL FAILURE OF UPPER EVAPORATOR BLOWER. SYSTEM DEACTIVATED AND DEFERRED IAW MEL. AIRCRAFT RETURNED TO BASE WITH NO FURTHER (SMELL). LATER, CHANGED UPPER EVAPORATOR BLOWER.