When range in union IF sentence does not work

Im trying to look at multiple ranges and check each cells with an if sentence in order to replace letters with words e.g. If the cells reads "AR" replace it with "Night"..This works perfectly if I say Range("D10:D40") but not if i say Union(Range("D10:D40"), Range("L10:L40"), Range("T10:T40")...Then it says 'Type mismatch' error 2042...

 For Each cell In Range("D10:D40")
    If cell.Value = "NR" Then
        cell.Value = "Nat"
    End If
Next cell

 For Each cell In Union(Range("D10:D40"), Range("L10:L40"), Range("T10:T40"), Range("D49:D79"), Range("L49:L79"), Range("T49:T79"), Range("D88:D117"), Range("L88:L117"), Range("T88:T117"), Range("D127:D153"), Range("L127:L157"), Range("T127:T157"))
    If cell.Value = "AR" Then
        cell.Value = "Aften"
    End If
Next cell