Rob
Ansys Employee

When you move between codes check the sizes. As you've found the scale can get messed up. My approach is to mesh to whatever size the geometry thinks it is (mm, m, km) and in Fluent scale the mesh. Scaling CAD tends to cause problems with the tolerance controls, whereas the mesh doesn't have that issue. 

Note, changing the units in Fluent just changes the reporting, you need to scale the mesh.