What was found
DURING PREFLIGHT WITH THE APU RUNNING & BLEED AIR ON THERE WAS NO COLD AIR BEING PRODUCED. AFTER SELECTING A COLDER TEMP & AIR SOURCE TO HIGH WITHIN A MINUTE THERE WAS A POOF SOUND & THE CABIN FILLED WITH A STRONG SMOKE & ELECT SMELL. ACM OVERHEAT ANNUNCIATOR FLASHED & THE APU SHUTDOWN. TROUBLE SHOT FOUND APU BLEED VLV STUCK IN MAX COOL POSITION CAUSING ACM TO SEIZE. R & R ACM IAW MM 2215460 & 2341316 CHAP 2-2-04 & INSTALLED BLEED SHUT OFF VLV IAW MM CHAP 36-12-00. NEW SEAL PN 460-200 & MS9068-032. OPERATIONS & LEAK CHECKED GOOD.