In 1937 the initial order was made for two diesel luggage railcars. Difficulties during production led to the modification of the order and it was turned in to the construction of two Locomotives. Shortly before the opening of the «Landesausstellung» 1939 in Zürich the first of two was delivered, the Am 4/4 1001. The second, Am 4/4 1002, was delivered shortly after.
No more engines from this type were built. On the other hand, various subassemblies became groundbreaking for subsequent vehicle series. This type of locomotive was used to derive the design of the gas turbines locomotive, Am 4/6 1101, delivered in 1941.
The locomotives were rebuilt in 1962/1963 in the HW Zurich. They got new gearboxes, a foreign ventilation for the drive motors and a nozzle ventilation grille. The maximum speed was reduced from 110 km/h to 75 km/h.
At the same time the machines were renumbered Bm4/4 II 18451 and 18452.
Field of application and depot affiliation of the locomotive 18451
- 1939 Exposition at the Expo 39 „Landi“ in Zürich
- 1939-1940 Winterthur, commissioning
- 1941-1943 Storage in depot due to fuel shortage
- 1944-1946 Lausanne, Broye-Linie
- 1947-1960 Geneva, Line Geneva - La Plaine
- 1960-1969 Winterthur, Line Etzwilen - Singen
- 1969-1990 Winterthur, Auxiliary Locomotive and special trips
- 1990 Historical vehicle, Depot Olten
- Care by Team 10439 Historische Loks Olten