All the East-West trains were fully air-conditioned (except baggage cars, RPO's, etc.) by the late 1930s, although -- I'd have to check some Official Guides -- until about 1939 they hedged the equipment listings in the timetables with "regularly assigned cars air-conditioned." Each car had a cooling unit powered by a generator driven by a belt which ran off the axle of one of the trucks; when speed dropped below 15 mph, batteries took over, which would be recharged when the speed again reached and exceeded 15 mph. If the train had to stop for an extended period or for some reason had to operate at restricted speed for an appreciable distance, the cars got hot when the batteries ran down.
