While in operational service, a number of changes were made to the vehicles. When first delivered, Wedglock automatic couplers were fitted to the motor cars in the middle of the train, which provided mechanical, pneumatic and electrical connection. The motor cars at the outside ends of the units were only fitted with mechanical couplers. These were changed to Wedglock couplers as part of the work to make them compatible with the 1959 Stock. The renumbering of the cars into the same series as the 1959 Stock took place in 1965. In 1971–72, stabling lights were fitted, located at the bottom right of the five headcode lamps, and in 1989, the headcode lights were replaced by two headlights, although the placement was somewhat different to that of the 1959 Stock.