They were built by English Electric and the New Zealand Railways Department (NZR) between 1938 and 1940, and hauled mainly passenger trains on the Wellington region's 1500 V DC electrification, and banked freight trains on the steep section between Paekākāriki and Pukerua Bay.

[7][8] By December 1939 the assembly of four locomotives at the Hutt Workshops had been completed, and they were expected to be operating to Paekakariki early in the new year.

[16] They were shut down or removed in 1950 due to "ongoing reliability problems"; air turbulence particularly in tunnels or when trains passed on double-track sections resulted in downdraughts affecting the boiler and in passenger discomfort in winter.

In June 1951 the Deputy Mechanical Engineer said that the cost of fitting suitable boilers for the section from Paekākāriki to Wellington was not warranted as the carriages leaving Paekākāriki had residual heat, and a steam loco could pre-heat carriages before they left Wellington.

In 1954-55 two boilers were installed in the Wellington station basement (and in 1958 one went to the NZR Road Services garage in Rotorua).

A porter-shunter at Johnsonville was accidentally killed in March 1940 when he stepped into the path of a train being shunted by an ED locomotive.