What was found
IAH- FLIGHT 3906, THE CREW NOTED A STRONG SMOKE SMELL WHEN CLEARED INTO POSITION AND HOLD.SMELLED ELECTRICAL IN NATURE, AND, OCCURED AFTER ALL LIGHTS WERE TURNED ON. IAH- MAINTENANCE FOUND PACK #1 OVERHEAT MESSAGE ON EICAS. MAINTENANCE REMOVED AND REPLACED THE #1 ACM, PERFORMED A OPERATIONAL CHECK, NO DEFECTS NOTED, AND, THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.