The American Locomotive Company ("Alco") built the FA-2, and matching B-units, from late 1950 through 1956. They were very similar to the FA-1/FB-1 units produced, except that the diesel motor, a 12-cylinder model 244, was upgraded from 1,500hp to 1,600hp. The FA-2 models were also lengthened to add a steam generator needed for passenger service. The big problem with the FA-1 and FA-2 locomotives was the 244 engine. It broke down easily, and tarnished Alco's reputation. The Pennsylvania Railroad ran the FA-2 models in an A-B-A configuration, fairly permanently coupled. This gave the consist a total of 4,800hp.
The photo of PRR 9614 from my personal collection.
Originally these engines were classified as PRR AF-3a, but in 1951 they were re-classified as AF-16 (Alco, Freight, 1600hp). These engines were all used in the PRR's Central Region. The idea was that since these engines broke down regularly, they were all grouped in the same area, so that mechanics could develop the know-how to fix them quickly. The Pennsy owned 24 FA-2, and 12 FB-2 engines (i.e. twelve A-B-A consists). By the late 1950s they were all moved to the Pittsburgh area. All were traded back into Alco for new road switcher engines before the Penn Central merger.