Q: Can one decoder be wired to run two engines, such as an A-B unit that do not get separated?
A: Yes, as long as the current capacity of the decoder is not exceeded. We recommend that you check the stall current of both locomotives before installing a decoder that will handle both.
Note that you can control two locomotives with decoders as a consist or MU lash-up so that you do not have to use a single decoder to control both locos.
Issues we have seen with using a single decoder to run two locos together:
1. Make sure your wiring between the two locos is secure and flexible. If the wires are too large or too long, you may experience binding. If you don't provide for strain relief, your connection may be broken during handling of the locos.
2. Using one decoder to operate two locomotives does not guarantee that both units will run at the same speed because of the differences in the operating performance of the two locomotive's mechanisms. When you use a single decoder in each locomotive, you can adjust their performance characteristics by speed matching so that they will run well in a consist. We recommend using one decoder for two locos that have similar performance characteristics that do not need adjustment.