Which 163 series decoder do you have? As per NMRA specs, the Blue wire is the common for the lighting system. But, ditch lights in an Athearn are 1.5v not 12-16, and will burn extremely bright for about .25 secs.
ops:
But anyway, the 163 series are only a 3 function decoder and 1st function is forward lights, 2nd is reverse, 3rd functionless. You would need a 4 function or better decoder for realistic flashing effects.
I put this decoder in my SD70m,
http://www.tcsdcc.com/decoder/A6X.htm
A TCS A6X, which completely replaces the onboard controller. It also supplies the 1.5v for the Athearn lights, with an onboard voltage regulator. It is a 6 function output decoder. So when I get a chance, and feel froggy, I'll wire up 2 more ditch lights on the rear and controll them with it.:thumb:
Edit: that decoder costed $23 at dccroundhouse.com
Edit: OOps, it is a 6 function decoder
from Digitrax's instructions:
F3 and F4 are also available on the decoder board. These can be accessed by
snipping the shrink wrap and peeling it back to expose the solder pads that control
these functions (Figure 2). To use these functions, solder a wire from the
pad for the function you wish to use to the lamp (or other function) you wish to
control. The Blue/+Common pad works the same way as the blue wire on the
harness and is provided here for convenience.
The instruction pdf is here; http://www.digitrax.com/ftp/dh163d.pdf