What was found
ON FINAL APPROACH WHILE PASSING 2000 FEET, CREW SMELLED A BURNING ODOR ON THE FLIGHT DECK. CAPTAIN NOTICED A MOMENTARY PUFF OF SMOKE THAT DISSIPATED QUICKLY. ODOR SEEMED TO DISSIPATE, THEN SEEMED TO RETURN ON TAXI IN. NO VISIBLE SMOKE OR ODOR DETECTED IN PASSENGER CABIN. MTC. FOUND LT RWY TURNOFF LIGHT SWITCH FAILED/BURNED. REPLACED L RUNWAY TURNOFF SWITCH S1 PER WDM 33-42-21. CHECKS GOOD.