I have a Spectrum desiel loco that is DCC on board. When it is parked on a side track for no reason it will take off on its own. You never know when. It only happens when other loco's are running. I had to isolate the side track with a insulated rail jointer and a seperate switch to keep this loco in its place. I tried to re-program but it still takes off on its own. It responds to its address and runs fine when called upon. Is the decoder bad. It only has about 30 min. run time.
Let me ask, just to make sure. You are running on a dcc system and not DC?
Yes my layout is DCC. My controler is a MRC Prodigy Advanced 2 Squared, 3.5 amp. This loco has a mind of its own when it's setting idle on a side track. It just takes off when it wants to. This loco is the only one out of 15 loco's that I have does this. My 4 other Bachmann's are ok on this layout.
First, are you certain that everything DCC controlled in you layout has a different address than the decoder in this engine.
You are certain? Good.
Maybe the decoder is bad. One experiment to help isolate the source of the problem would be to change the decoder address. Verify the engine responds to the new address and not to the old one. Does the engine still misbehave when others are running? If not, maybe the problem was not in the decoder.
Now program another engine to the same address the previously misbehaving one had. Does *that* engine now misbehave when you are running others?
I have a similar problem. When running two DCC locos at the same time, one will continue moving after I close the throttle. I slow the speed slowly then, off completely, and sometimes it will maintain the last slow speed for about a second to a sencond-and-half, but no more than two seconds. However, it only does it when both locos are going foward or reverse. When one is forward and the other is reverse, the one that acts up will sometimes try to change directions and then back again. But it only does this when it is under the control and the speed knob is around the same slow speed. Other than that, I have no problems at all.
Arcing between wheels and rails can cause locomotives to receive false signals or no signals at all. This is exacerbated by inadequate wiring. Some decoders are more sensitive to this than others. If the filter capacitor on the decoder has failed, it becomes really, really sensitive to static.
The solution is to clean the rails and locomotive wheels, then add one drop of conductive oil to each rail and let the train spread it around. Even better, but more work, put a few drops of conductive oil on a small square of cotton cloth and spread the oil manually. Even if the oil is only a few molecules thick, it will suppress arcing. And when the oil is that thin, it has little to no effect on traction. With arcing suppressed, one of the worst sources of rail and wheel contamination is removed. Conducta-lube, Hobee lube and Labelle #108 are all listed by their manufacturers as conductive oils. Wahl hair clipper oil will do the same thing. I have been doing this for decades on the mixed nickel-silver, brass and steel rails on my layout and rarely have a stall or even a headlight flicker. Try it - you'll like it. But remember, just one drop on the rails or just a few drops on a piece of cotton rag. More is definitely NOT better.