What was found
A BURNING ODOR WAS DETECTED IN THE COCKPIT DURING AN AIR AMBULANCE FLIGHT 10 MINUTES OUT. CREW MEMBERS CONFIRMED ODOR. ATC CONTACTED AND ADVISED OF THE EVENT AND FLIGHT DIVERTED. MX SEARCHED ACFT FOR EVIDENCE OF BURNING, NOTHING WAS FOUND. PERFORMED A 20 MINUTE GROUND RUN WITH FULL ELECTRICAL LOAD NO DEFECTS NOTED, THEN PERFORMED A 20 MINUTE OPS CHECK FLIGHT WHICH WAS SATISFACTORY. COULD NOT DUPLICATE THE PROBLEM AND RETURNED ACFT TO SERVICE.