On Monday my Auscision XPT was delivered. So in order to give the coaches a run, I set them up behind a loco as I had not yet installed the decoders into the power cars. The XPT coaches kept derailing at various points on the layout. Upon closer inspection, I had to loosen the bogie screws by about a quarter turn and that fixed the issue. After dinner that night, I installed the TCS EU621 decoders into the power cars. I put them on the track set the first power car to forward hit the headlight button and incremented the speed and it ran in reverse with the red marker lights lit. So I put the loco into reverse and it ran forward with the white headlights lit. Function 1 turns on the flashing strobes on the roof. The second power car behaved similarly.
Well tonight I got down to the shed and set up CV22 in each loco. This controls how certain functions (F0F and F0R - front headlight and rear lights) are handled while the locos are in a consist. But setting this to a value of 3 the headlights and red marker lights will work in a consist. So I made a consist of my two locos. The power cars were numbered 2012 and 2017. Now I use the NCE DCC system and it is simply the best out there in my opinion. Now remembering that the locos run in reverse direction to the way they should, I made up an advanced consist with 2012 as the front power car and said it was running in reverse. I then added the rear power car as 2017 and said it was running in forward direction. We know that this was not correct but if you do, the power cars behave correctly. When you select 2012, and hit forward and turn the headlights on, the white headlights in 2012 come on and the red marker lights in 2017 come on. If I hit reverse, the lights change around correctly. However, if you were to drive your XPT back the other way for any extended distance, I believe that you should select the other power car as the loco to drive and select its headlight. But either way, the lights still work correctly.
So this is how to solve the issue with the incorrectly wired headlights in the Auscision XPT. Quite simply really.