What was found
COCKPIT HAD A BURNING ODOR, FA DID NOT NOTICE IN CABIN, SEEMS WORSE WITH HP VALVES OPEN. ODOR CONSTANT DURING FLIGHT LOWER ALTITUDE, THE WORSE THE ODOR. INSPECTED PNEUMATIC LINES FROM LEFT ENGINE. PERFORMED OPERATIONAL CHECK OF THE AIR DISTRIBUTION IN FLIGHT COMPARTMENT, AND OPERATION CHECKED THE AIR CONDITION SYSTEM, COULD NOT DETECT ANY BURNING ODORS, OPS CHECKED GOOD.