Model Loco changing speeds on it's own

[lardenr]

Hi,

I'm helping a friend out with an issue he has on his N gauge layout. He just recently purchased a class 37 Graham Farish loco. Put in a 6 pin decoder. All works well at the start, a nice slow start, but there is one part of the track, that it just briefly stops, and then goes off at full speed round the track, and even if you alter the speed it stays at the constant speed. Only when you emergency stop, it stops. The you start it again, goes ok, then hits the same track, and off it goes again. Anyone else had this issue? could it be an issue with the decoder?

Many thanks in advance.

[Steve M]

You say it happens at one particular spot on the layout. I would suspect a short at that spot causing the decoder to think it's running on DC and going into an uncontrollable DC runaway.

[Rog (RJ)]

Dirty track could be the cause.

[lardenr]

Many thanks, the track is very clean, but I have been suspecting it's short circuiting and sending it mad, so you may have just confirmed it for me.

[RAF96]

Disable DC running in CV29.