If there is no change in current draw with the engine track connected to the transformer, you're likely looking for a power supply issue from the track to the board. When you first post the PS/3 board, you should get a noticeable power surge as it charges the supercaps, even a cheap ammeter should be able to see that. Typically, I see a peak of around half an amp or so and then it tapers off to more like 1/10 of an amp when the cap has charged.
The reason I mention that switch is it's a cheap switch and it's frequently the problem with this kind of issue.
Does it act the same if you put it on a test track with just a transformer, no DCS signal?
