I stand corrected.... I have a couple of other units that I have had (so far) reviewed... A couple others that I shot in December 2005 seem to have the same box... Harold
That's interesting... the only units I have spotted it on (in my photos) are older D940-CW's.... Harold
In theory, the APU allows the prime mover to automatically shut down after a brief idle period to reduce emissions. The small pony motor then kicks on as needed to keep the batteries charged and oil and water warm without burning as much fuel as the main engine. The new units have auto-start that fires everything back up if you move the reverser or throttle but most of the add-on packs have to be started manually at the start station in back. It's a lot of plumbing and wiring that seems to not be real reliable yet.
Dont they usually place the APU's within the engine compartment? Looks more like a add-on DPU unit? Or more processor power,Apple/Mac? lol.
I don't have a clue, but I'm sticking with my theory that it is a radar detector package so the train doesn't blast through a speed trap.
On older GMs the APU is in the back behind the air compressor. No room back there on the GEs so they stuck them on the walkway.
If it stays on many parts of NS, it won't have to worry about "speeding" Harold </font>[/QUOTE]It usually is in unfamiliar territory when you most need such a device.