Each decoder must be separately wired for the functions to work. Except for having the same track pick-up power connections there should be no wires or power sharing between the decoders. Connecting the commons of the decoders together is just asking for trouble.
---In WiringForDCC@..., <pcgumshoe@...> wrote :
I'm not a fan of the Loksound 4.0's volume level so I opted to purchase a non-sound unit and install a Loksound Select with a secondary decoder for the marker lights. This has proven to be almost impossible. For one, I have to combine the common wire from both decoders (or do I). I can get headlights, number boards and beacon, but they are all on the Loksound Decoder. The secondary decoder, a TCS A6X won't put out any light.