Hi

I have the above loco and am having issues which I am struggling to understand.

Initial the loco horn would have an uncommanded start and I would have to remove power to the loco to stop it. I did a decoder reset and that seemed to clear the problem for a short time.

This weekend, the loco has started to move, at a very slow speed, on its own as soon as power is applied to the track. No other locos show this trait!

I have checked the app on my iPhone and the speed controller is at zero. The issue also occurs when my iPhone is switched off, so I cant see that it's the app that is causing the problem. I am running the Z21 (black)

Is it likely to be a decoder issue? Whilst the loco is still under warranty, I dont really want the fuss of sending it back to Marklin for repairs, and would rather swap the decoder out for a Loksound, if there is an equivalent as it would then be common with other of my locos.

I would welcome any thoughts members might have - thanks

Alex

Hi Alex
Of course decoders may become "crazy" (start undesired commands, etc) but occurences are very rare I think.
To be absolutely sure, I recommend to repeat the test with a steup as simple as possible:
- only one loco on the SIMPLE track (loop?)
- only one simple command unit (which one is it for you? CS3, CS2, MS2) without any external device smartphone, app, etc.
- does the behaviour presists?
- when operating the loco in analogue does it do funny things?

In my experience, often funny behaviour is more often than not, caused by distorted digital signal (remote short circuit, capacitor on the track, etc).
Your loco is rather recent (2023 or later) so a recent mSD3 normally is not prone to do things like this but as I said earlier a faulty component inside the decoder (e.g.: poor filtering by a failing capacitor) may cause this.
In my many Märklin digital locos (60 or so) I have noticed that some are much more sensible (receptive) to electrical perturbations and the occurrence is often coupled with a poor digital feed in this part of the layout.
Cheers
Jean

Hi Jean - thanks for your post

I would agree that modern electronics are very reliable and not prone to failure like this, so I am happy to accept that it could be something like distorted digital signal.. however, I set up a test track away from everything else and the moment I put the loco on the track it started to move.

Alex

Since you have a Z21 I assume you are using DCC. I also think that the DCC address is unique. But, does the decoder still have MM and mfx protocols enabled? I would disable them as well as analogue. Analogue is disabled with zero to CV29 bit 2 as far as I remember. I don’t remember how to disable MM and mfx.

What is a Z21? Not familiar with it. One of the odd features I was told about the mfx decoders is that they seem to retain some settings. For example I changed the name of a Marklin mfx loco as I always do and when I set it on a friends layout his CS3 had the name change. I am not sure what information is retained.
Well I just tried it with a mfx and mfx+ loco and they did not move. So the speed is not retained. Perhaps you have some speed set on a controller.

Hi, and thanks for the post

My total layout is about 38 metres so not very big - 3m x 2.4 approx. yes I do have a power bus - sounds like the same sort of issues.

The Z21 is the DCC controller.

Thanks Dave. I guess I will stick with my $29.00 router and iPad. That even allows me to operate switches.