What was found
CREW REPORT: ALT EQUIP COOLING FAN INTERMITTENT AT FL250 SAMC TEXT: PACKS AND CABIN PRESSURIZATION NORMAL, ALT EQUIP COOLING EXHAUST FAN 'OFF' LIGHT FLICKERING ON INTERMITTANTLY. FOUND EXHAUST DUCT FORWARD OF MUFFLER CLOGGED WITH DUST AND DIRT RESTRICTING EXHAUST AIRFLOW PAST SENSOR M100. REPLACED SENSOR PRECAUTIONARY AND BLEW THE DUCT FREE OF DUST AND DIRT. FLOW FOUND SATISFACTORY. ALL ELECTRICAL CHECKS OF THE FANS NORMAL AND ALTERNATE WERE FOUND NORMAL.