My "N" Scale F7a will not respond to the decoder. Programer shows "No responce from decoder", but when I turn off the programer track the unit moves forward by itself with no input from the comand station!
Have you tried doing a reset ? CV 8 to 8 .
There seems to be some problem with the decoders in these things. I have only two with the factory "smart" decoders, but both of them have fried on DC after brief use. I am not a DCC user. Fortunately, it is not difficult to remove the decoders and wire around where they were.
It could be that your DCC system can't recognize the decoder. If you are using a Digitrax system, you need to place a 1K-ohm resistor (any wattage) across the programming track (really anywhere in the circuit across the two leads) and that should solve the problem. I have mainly Bachmann engines and the ones that have the factory decoders all require this. Be sure to remove the resistor when you are done programming. In order to make it easy on myself, I cut a small test lead in half and soldered each end to the resistor so I can clip it onto the tracks using the alligator clips. This assumes that your programming track is isolated from the rest of the layout. Hope this helps.
Fred Klein
Okeechobee, FL