During the 1960s, the new El 13 locomotives were delivered, and locomotive-hauled express trains replaced the multiple units. From 28 May 1967, Class 66 was moved to serve the Vestfold Line. It operated in services to Skien until 3 June 1973, after which it only served to Larvik. During the summer of 1975, they could also be seen operating Oslo V – Nelaug, and during the fall of 1976 on Oslo V – Drammen. The units were taken out of service on 21 May 1977. A single motor car, 66.01, has been preserved by the Norwegian Railway Museum, who has stationed it at Elverum Station.