In a data structure, which stores information about the source zones, the zone names are expected to be not longer than 50 characters. The longer names corrupt this structure, and the code fails to work because of a memory error. For example, consider two surfaces with ids 279 and 3, respectively. Consider that the name of the surface with id 279 is wall_blower_zone-wall_strips-rest… and that with id 3 is wall_blower_zone-wall_strips-rest…-shadow. Since these are longer than 50 characters, there will be memory error associated with the source zone data structure asd file. For now the work around is Read the case file and rename the two wall zones id=279 wall_blower_zone-wall_strips-rest… and id=3 wall_blower_zone-wall_strips-rest…-shadow to much shorter names, not exceeding the 50 characters length limit. Then write the case file. Restart Fluent and read the new case file (write and re-read is important!). Then Fluent will be able to import your ASD files.