You must always indicate the sheet you intend to work on.
This instruction, does NOT select the range as you think, because it reads the active sheet which is not TCU but is Sheet1.
Code:
For Each c In Range("F15:F" & Cells(Rows.Count, 6).End(xlUp).Row)
so you should be write:
Code:
For Each c In ws.Range("F15:F" & Cells(ws.Rows.Count, 6).End(xlUp).Row)
and so on...