Hornby tender-drive loco problem

We have a 2003 Hornby Flying Scotsman. When we put it on the track and power up, it moves sometimes no distance, sometimes up to six inches, then the controller shuts down.

That sounds to me like a short but I can't see any evidence of where the problem lies. I've lifted the covers off and it ran OK with them off for a while, which is suggestive of a connection problem of some sort I guess, or maybe a loose wire. But everything looks fine.

The model is less than a year old so I can return it under warranty, but before I do does anyone know of an easy fix? Somewhere wires routinely trap or chafe? A soldered joint which is prone to failure?

I am electrically competent, by the way - I have a B Eng in electrical engineering.

Apologies if this is a Well Known Problem - I did Google and came up blank, but I am notoriously bad at Googling for non-Linux issues

Does the loco have 2 thin 'prongs' on top of the connector to the tender?
If so then widen the gap between them. My guess is that one of these prongs is touching the post on the tender and causing a short.

Thanks for that - I thought I was smarter than that

It turns out that one of the prongs was just catching under the insulator - it worked without the cover because I put it on the track, and it failed with the cover because my nine-year-old put it on! I assembled a test track on a table with good lighting, got Michael to put the loco on the track, and all became clear.

It does seem to run better for the really thorough cleaning it got while trying to diagnose the problem!

Call myself an engineer? D'oh!

"Guy Chapman" wrote

Sounds like a faulty thermal cut-out in the controller to me. If you can borrow another controller and the loco works fine with that, then my diagnosis is confirmed.

Yes, the problem Len described happened to me with a Battle of Britain. Good luck
Does the loco have 2 thin 'prongs' on top of the connector to the tender?
If so then widen the gap between them. My guess is that one of these prongs is touching the post on the tender and causing a short.

I concur with the brush holder problem, it is a know problem to the trade on Hornby ringfield motored products made in China. The standard of detailing of the loco's has gone up, but quality control has gone down since the 1997 move to China. If this solution doesn't then you need to try another control unit as the safety cut out on the controller could be faulty. Another known fault is the ringfield magnet not being put into the motor casing correctly and at an angle, 2003-04 China made Hornby A3's and A4's are known to suffer from this problem. It causes the armature to jam abd the loco to stop after running a distance. It's a known quality control problem.