DCC loco. with loose wire

[ROY0147]

I am hoping that some kind person will be able to help me please?
My Hornby R1075 Jinty Class 3F tank 'oo' gauge loco has dcc fitted and it runs well on my dc layout.
I am getting a dcc layout soon but, on inspection I see there is a loose brown wire coming from the chip area and I am sure it should be connected but where?
It looks like it is long enough to join at one side of the capacitor but I am wary of trying anything without some advice!
I have taken a couple of pictures which I hope will help.
Thanks in advance.
Roy

[cadman]

@Roy........this loco has been rewired to run specifically on DC only......note the two black wires connected to the motor, these feed directly from the pick-ups and should not be there if DCC is to be used. That's why the orange wire has been disconnected. If you solder the orange wire to the motor now and run on a DCC controller you will instantly destroy the decoder.

[ROY0147]

Thank you for the timely warning - I am pleased that I didn't try connecting to dcc yet!
I wonder why someone would wire it for dc only, could the decoder be faulty?
I thought with some types of decoder you could run on dc without any alteration and then on dcc as required.
Presumably I can't check the decoder without removing the 2 black wires, leave the grey on one pick-up and connect the stray orange wire to the other pick-up.
If I did this would I now not be able to run on dc with this type of decoder or if it was faulty?
I don't want to cause more problems as it does run very nicely on dc.
I apologise for my ignorance on dcc matters and for asking so many questions.

[Walkingthedog]

Perhaps they purchased the DCC loco second hand and didn’t want anything to do with DCC so bypassed the decoder. They left it in place to make it easier to resell.
I had several DCC locos that ran beautifully on DC. One even had limited sound.

[Brian]

Thank you for the timely warning - I am pleased that I didn't try connecting to dcc yet!
I wonder why someone would wire it for dc only, could the decoder be faulty?
I thought with some types of decoder you could run on dc without any alteration and then on dcc as required.
Presumably I can't check the decoder without removing the 2 black wires, leave the grey on one pick-up and connect the stray orange wire to the other pick-up.
If I did this would I now not be able to run on dc with this type of decoder or if it was faulty?
I don't want to cause more problems as it does run very nicely on dc.
I apologise for my ignorance on dcc matters and for asking so many questions.

Hi.
99% of all loco DCC decoders can run on DC rail power, so long as CV29 setting values haven't been adjusted to disconnect DC operation. This can only be checked, assuming the loco with the decoder connected does not run on DC, by a DCC system that's able to set and ideally read CV values. CV = Configuration Variable. Sort of fine-tuning slots in the decoders electronic chip.

ON NO ACCOUT allow DC rail power to get to the decoders Orange and Grey wires. If it does then the decoder will be destroyed! For DCC operation - You MUST remove all direct wheel / rail wiring on the motor before connecting the decoders Grey and Orange wires.

To test the decoder is OK you will ideally need a DCC control system. Then remove the two wires on the motor coming from the wheels and in their place connect the decoder Grey and Orange wires to the motor (Doest at this time matter which way around they are connected). Ensure the removed wires cannot touch anything, so ideally place some PVC tape over their ends. Next, ensure the decoders Red and Black wires are connected to the wheel pick ups. Assuming they are connected, then place the loco onto the DCC Programming track and read CV1 (address) Normally it is set to 03. But may have been set to anything in the range 1 to 9999! Hence reading CV1 to gain the address. Once the DCC address is known remove loco form the programming track and test it on the main tracks using the DCC address number found previously.
If you can't read CVs on a DCC system, try a decoder reset - Usually CV8 then enter a value of 8 will reset the decoder to its default settings including address number 03.

What to do if you don't have a DCC system? Remove the decoder completely and rewire directly wheel(s) / pick ups to the motor on each side. Or as per your images, remove both the Grey and Orange decoder wires from the motor and tape up their ends ensuring they can't get caught in any moving parts, then leave the two direct feed wires on the motor coming from the wheels/pick ups. The loco now will only operate on DC power. But it's always best if just DC operation is need to completely remove the decoder.

[ROY0147]

Thank you for such a detailed reply. I can now see what all the different wires are for.
I don't have a suitable dcc control system - the controller that is in the post is only a Hornby Select which, I understand, is very limited and would not be able to read CVs probably.
In the interim I will probably have to accept only dc operation and I will make sure none of the decoder wires are able to make contacts anywhere.
Regards,
Roy

[RAF96]

- the controller that is in the post is only a Hornby Select which, I understand, is very limited and would not be able to read CVs probably.

Not so - The Select can be updated if required by Hornby (return to works) for a modest sum (£15) and it will be able to write CVs but not read them as it effectively programs on the main. Check the current rev state by watching for xx - 30 - 03 at power up. Xx = the rev state. You need 16 - aka v1.6. There is a facelift version that will show 20 - 30 - 03 aka v2.0 which is functionally identical to v1.6, just a different internal chipset.