Backup / Reverse Light Wiring for Postwar Engines

The 8506 switcher simply has the bulb grounded in the tender, and the other lead tethered to one motor brush(the one that glows bright in reverse).  The bulb also glows dimly at higher throttle settings while going forward.

I just added a 12V incandescent backup light to one of my PW whistle tenders.

It was actually really simple.  Solder one lead wire to the brush on the motor that shows a positive AC voltage between it and the solder lug on the e-unit that gathers several of the wires on the top side of the e-unit while the motor is running in reverse.  Solder the other lead to that lug. 

I made a little tether connector using a molex 2-pin Spox from leftover MTH stuff.

The downside is that it is dim at slow speeds.  You could probably use that power connection to run a small constant voltage board in the tender instead, then just wire an LED to those outputs of the CV board.  I actually have a CV board in my tender connected to the track power picked up by the tender, but that runs my always-on marker lights in the tender.

I'm pretty sure it's possible to do it, but it's hard to explain how. You would want to solder the wires to one of the reverse unit outputs - the simplest way to figure out which is just by testing it. Put the locomotive in reverse with it suspended on blocks so that it doesn't drive off, and touch the wire to each of the outputs until it lights up. I've never done this myself, but it seems feasible.

I actually have a locomotive with this feature - a General Models NW2 from the late 40s. It has a very different style reverse unit from a Lionel, but it's set up to where it will only light up in the direction of travel.

Rob, Jeff, Mr. Beere, thanks for your input.  Perhaps the reason there are no diagrams is because it is so simple, although it does sound like a couple of ways to do it.

If I understand correctly, with Rob's method, your are using the e-unit to switch center rail power on/off, as the bulb socket is grounded.

With Jeff's method, you are using the e-unit to switch the ground/common on/off as the center rail power is always available at the socket (from the solder lug).  If that's the case, I'm guessing the socket is isolated from the frame in some way?

In every locomotive I've worked on, the sockets are grounded to the frame and have a wire coming off them to be connected to positive somewhere.

Here's a crude illustration of where it needs to attach to - one of these sets of fingers will be positive while in reverse. When going forwards, that same set of fingers will be grounded, and therefore the light will be off. You just need to figure out which set is the right one, and solder the positive wire from the light to it.

I've never done this before, so I can't guarantee it will work, but it seems straight forward to me.

To clarify, in my method there was no socket.  I soldered wires directly to a 3mm 12V incandescent bulb (looks like a grain of wheat bulb).  I drilled up into the "backup light" housing (which was just a solid piece of plastic molded into the tender) and inserted the bulb right into the plastic and secured inside with a dab of glue.  The bulb wires are affixed to the molex connector that I epoxied at the front end of the tether.  No interaction at all with the ground wires that feed the air whistle. 

I suppose I could have tied one of the wires to ground through the tender, but I had 2 pins in the connector so I instinctively used both of them.

@Johnbeere posted:

In every locomotive I've worked on, the sockets are grounded to the frame and have a wire coming off them to be connected to positive somewhere.

Here's a crude illustration of where it needs to attach to - one of these sets of fingers will be positive while in reverse. When going forwards, that same set of fingers will be grounded, and therefore the light will be off. You just need to figure out which set is the right one, and solder the positive wire from the light to it.

I've never done this before, so I can't guarantee it will work, but it seems straight forward to me.

You just drew the exact same connection points I describe here!

@ADCX Rob posted:

The 8506 switcher simply has the bulb grounded in the tender, and the other lead tethered to one motor brush(the one that glows bright in reverse).  The bulb also glows dimly at higher throttle settings while going forward.

Seems that that setup is the way to go then - I didn't realize you had already described it, just in a different way.