The 40 locomotives that were not converted to the DC class continued in service throughout most of the 1980s. The combination of the deregulation of land transport and the decline in rail freight volumes, reduced inter-regional passenger numbers, and the electrification of the NIMT saw them become surplus to requirements. Due to tunnel clearance problems on North Auckland Line through the Makarau Tunnel which prevented DC locomotives working in Northland, twelve DA class locomotives were given an "A grade" overhaul in 1980 with some modifications to improve crew comfort. They were painted in International Orange colours at the same time.