I have read all the posts regarding the operation of the red Mars light on these models. I offer this fix as a temporary fix until Lionel comes up with their fix. Here goes:
1. On my Lionel Legacy PRR J-1 the cab light is on when the engine is stopped. It goes out when the engine is moved, either forward or reverse.
2. What if the cab light is unplugged and in its place the Mars light plug is inserted into that board (one might have to lengthen/shorten wires). Then the MARS light will operate as the cab light.
3. This work is to be done ONLY by Lionel technicians.
4. I do not know if the plugs for these 2 different light are compatible or if they draw the same electric power; Lionel will know this.
5. If doable, then the cab light feature is not available.
There is a good chance that this idea has been floated around and found not workable. If so, I apologize.
Steve