During 1997, there were five incidents where NSB's Nordic Mobile Telephone equipment interfered with the locomotive's electronics, causing the emergency brakes to activate. This caused a temporary halt until the motorman had unlocked the brakes. The problem was fixed by moving NSB's mobile transmitters. The units were taken into use on the Bergen Line from 5 January 1997. Later they entered into use on the Dovre and Sørland Lines, and then on regional trains around Oslo, such as the Vestfold Line. In August 1998, NSB stated that El 18 used more power than some of the substation transformers along the line could handle, particularly along the Vestfold Line. Part of the problem was caused by a mechanism in the locomotives whereby the motor was turned off if the wheels spin. The result was that the full power output of the El 18 along parts of the railway network could not be utilized.