What was found
SMELL SIMILAR TO HORSE MANURE DURING PREFLIGHT WHEN USING EXTERNAL AIR CONDITIONING APU BLEED SUPPLYING BOTH PACKS AND APU BLEED SUPPLYING PACK 1 ONLY. NO SMELL WHEN USING APU BLEED TO SUPPLY PACK 2 ONLY. SEE ENCLOSED COS REPORTING SHEET-COS REPORTING SHEET IDENTIFIED SOURCE TO APU. PERFORMED FUME TO CABIN SMELL INSPECTION IAW TSM 49-00-00-810-921-A. NO DISCREPANCIES FOUND AT THIS TIME SEE NEXT ITEM FOR PACK DEFERRAL