dolphin diagnostic starts then stops no wires to timer in myu poiwer supply

by Frank
(Stamford ct)

I have a dolphin diagnostic. Its about 4 years old. The problem is it starts up moves a foot or two then goes in reverse for a few feet and then stops and then goes alittle more then stops and reverses back to the original direct. There is nothing stuck in the tracks, the motor seems to be working but it starts and stoops and reverses direction after about a half minute. I read somewhere that it could be the timer in the transformer. The transformer that they show is a little different in that mine does not have the same wires as the one I've seen on line. No obviouse wires to the timer or a yellow wire to connect to in mine