From time to time I have been involved in conversations about the BL2's, and whether they would, as delivered, MU with other BL2's or other EMD power? After a lot of research, a lot of help from Steve Dolzall and retired general foreman Bill Gorden, and some photographic support, I have now concluded the following.
All BL2's would MU, both electrically and pneumatically, with other BL2's and with F3's (and eventually the H15-44's). However, there were some differences in the locations of the jumper cable receptacles between the early BL2's and the later BL2's.
The early BL2's, units 30-35 all built in 4/48, had MU receptacles behind little doors high on the long hood ends, and beside the headlights on the short hood end, where MU cables could be plugged in. The locations of these doors are marked in the attached photos, both closed and open, with small red arrows.
At some point the Monon started relocating the MU recepticals to posts beside the handrail openings, both front and rear. This conversion no doubt happened between 4/48 and 4/49, because BL-2's 36, 37, and 38, built in 4/49, 5/49,and 5/49, came from the factory with these changes already made.
I have no documentation as to why the MU receptacles were moved, but it was probably done for convenience of the shop forces when they were assembling locomotive consists, and perhaps to permit the use of shorter MU cables between units.
Incidentally, Monon 30 was the very first BL-2 built and 38 was the last one ever built. / Ron
