DCC lighting help

[JRP]

I have an Athearn GP35 with Soundtraxx LC series decoder and am using 1.5 volt bulbs in front and rear (with resistors). I have been running it several days now and everything with the lights was working fine until I went to run it last night after tinkering with CV2, 3, and 4 for tuning voltage and speed, etc. . Now the lights go on and off as I add power to the command station whether the lights are on or off. I can turn them on and they stay on, but then when I add just a slight bit of power and the engine starts moving, they go off, then on and off again as I add more power. What does this mean? I have checked all the wires and they are all connected correctly. I didn't change anything under the hood that I remember. Any ideas? JRP (PS....Happy Turkey)

[CSX Robert]

The decoder is configured for 14 speed steps(CV 29 bit 1) and you have the command station sending 28 speed step commands.

[MisterBeasley]

Do the lights go on and off periodically, with a regularly-timed cycle, or is it random?

If it is a random thing, then it's probably a loose wire inside.  As the engine moves, it makes and breaks the contact.

But, the LC series decoders support some of the standard ligthing rules for prototype locomotives.  For example, the rear headlight on my Alco RSC-3 will flash while the engine is in motion, while the front headlight stays on.

[CSX Robert]

JRP

...I can turn them on and they stay on, but then when I add just a slight bit of power and the engine starts moving, they go off, then on and off again as I add more power...

A 14 speed step DCC packet has speed, direction, and headlight on/off information. A 28 speed step packet looks the same as a 14 speed step packet except that the headlight on/off bit doubles the number of speed steps(in 28 speed step mode, the headlight information is sent in a seperate packet). If the decoder is configured for 14 speed steps and the command station is sending 28 speed step packets, if you slowly increase the throttle from zero, the decoder interprets the packets as "speed 0, headlight off", "speed 0, headlight on", "speed 1, headlight off", "speed 1, headlight on", "speed 2, headlight off", "speed 2, headlight on"..., instead of "speed 0", "speed 1", "speed 2", "speed 3", "speed 4", "speed 5"...