What are these lights called and when should they come on????

They would come on if the engine is reversed.  But depending on if they are actually there, would not necessarily illuminate if the units were in a MU (lashup) because the nose of the engine in reverse would light in it's place.

Looking at the description from the Lionel site of the number you gave and the MSRP, I doubt there is a light or controlling board in these units.  But the number you gave is for a dummy B of a Delaware and Hudson Alco PB.  Are these the A units?  I think the number may be incorrect.

Thanks Marty. First, I do run them as a MU. The dummy A comes on when you first add track power, then goes off. I'll look at the powered A later and see what's up.

Jeff

Please check the numbers too.  The number you gave showed up as something else.  Not sure if it's the Lionel site or an incorrect number.  Are these Legacy?

My bad, 14568... They're TMCC.

I have a pair of TMCC FA2 AA's and the dummy A reverse light comes on at power up and goes off when the MU is addressed.

I suspect it has something to do with the back to back "lashup" of the AA with the dummy being told to start in forward  (which is actually reverse) so the reverse light comes on until the MU is addressed which tells it to turn off.

To elaborate on what Marty said, these rear lights should only come on when either unit is addressed with its seperate id# and put into reverse.

( Its a nice little mentioned feature that you can address each unit seperately and drop one or the other to use by itself)

Back to back units in an MU will toggel headlight based on the direction of MU travel.

Sometimes you see these backup lights on in MUs, this is likely because the operator has chosen to give both units the same id# instead of going through the extra step of individual id's added to a "lashup".

Thanks Rick! The manual doesn't address them at all so it appears I'm all good! Nice to know that's one less issue to be investigating.

I just ran the powered A alone and the back up light did come on. Amen!

RickO posted:

ometimes you see these backup lights on in MUs, this is likely because the operator has chosen to give both units the same id# instead of going through the extra step of individual id's added to a "lashup".

I always wondered about that.  Since each of my TMCC and Legacy locomotives has its own address, I never have any illuminated headlights between units in a "lash-up", bit I've noticed it in certain videos posted on the Forum by others.  Thanks for posting that answer.

Also note that proper MU addressing disables  the couplers between units. Only the front and back coupler of the MU functions.   MU consist act as a single unit, or should.   I had done classification marker lights on a set of  older Weaver E8's with EOB upgrades.   Front class lights green/ rear class lights red, using bi-polar LED's.  Hooked to the smoke unit out put,  the smoke unit terminals were not used for this E8 upgrade, the class lights would change color when the unit reversed. I had to do some internal wiring changes to get the MU E8's to properly change as a two unit MU.   

Mike - Now that's impressive!! 

Mike, that is slick!! 

At the time, Train America Studio's had a small kit, that could be purchased to do this using two lead, bi-polar, LED's

Wiring diagram.  Again note that you could not use the Smoke unit but these older models didn't have a smoke unit.

Mike, Thanks for posting the wiring diagram. That is a fun project.

You can do the bi-directional markers/class lights with the headlight/taillight TMCC signals pretty easily.  Here's a diagram of how I did that and more with the RMT BEEP that I upgraded when doing a beta test of the new ERR Cruise Commander Lite.  I figured it needed fancy lighting as well, so I went sort of all out.

As you can see, all of the LED's are driven from the two headlight outputs.  Included are the load resistors required for the R2LC light outputs with no resistive loads, you can also use .01uf capacitors, a better option.