The Y3 served the same purpose as the electric X9-series. A variation of configurations was used, with the production consisting of six motor cars, two cab cars and eleven trailers. With motor cars on each end the Y3 could have six trailers between. The Y3 was the first double decker used in Sweden. The series was prone to fires, since the cooling system didn't work sufficiently. This was solved through rebuilding the cooling system in the 1970s.