Not much to go on, there! Is the 125 a Hornby model? What's the Rxxx number, if known? What controller are you using? What happens if you put the dummy car on the track, but NOT connected to the power car? - As a new poster, you onl;y get two posts for the first couple of days, so don't waste your second post. Do NOT use the blue button with the white arrow, that merely repeats the last post. Scroll down to the empty white space, type your reply, and use the GREEN button that says reply.