What was found
UNABLE TO CONTROL ENVIRONMENTAL TEMPS IN ANY CONFIGURATION. HOLDING FOR TAKEOFF, CABIN & COCKPIT BECAME WARM. SELECTED MANUAL DID NOT ALLOW TEMP TO BE CONTROLLED. SELECTED APU BLEED AIR ON. SUPPLY TEMP STARTED TO RISE. A PUFF OF SMOKE FROM COPILOTS GASPER & ELECTRICAL BURNING ODOR SENSED IN COCKPIT. TURNED OFF COCKPIT RECIRC FAN, LT & RT ENGINE BLEEDS & APU BLEED AIR & RETURNED TO RAMP. SHUTDOWN, SELECTED APU BLEED AIR ON & TEMP ROSE ABOVE 250 DEGREES & CONTIUED TO RISE. E2 DISPLAYED ON AUTO TEMP CONTROL LED. WITH COCKPIT RECIRC FAN ON, A LOUD NOISE CAN BE HEARD IN COCKPIT. FOUND ECU COOLING TURBINE SEIZED. REPLACED COOLING TURBINE IAW MM 21-51-00. OPS AND LEAK CHECKED GOOD.