What was found
ON TAXI-OUT ACRID SMELL IN COCPIT, ALSO LIGHT TRACES OF SMOKE OR AIR PARTICLES UNDER MAP LIGHTS.CHECKED IAW FIM 21-00-01-301. C/OUT ENG RUN FOR 20 MIN BY CREW - NO SMOKE, SMELL ORLEAK DETECT. DURING ENG RUN WITH PACKS ON CHECKED WITH REC FANS, E&E COMP, LIGHTS & SWITCHES. ALL CHECKS FOUND SATIS. LANDING LT & ANTI COLLISION PNL LH WING SWITCH HAD BURN MARKS. REPLACED LANDING LT PNL IAW AMM 33-42-00.