Be careful!!!

Generally better not to twist wires together, but if needs must it should work well enough if you're careful. A dab of solder on the join would help. Then make sure it's all well insulated.

I'm not quite understanding the problem though. Presumably the black cable can be disconnected from the red connector? So what is it that's stopping you tucking it out of the way somewhere? What exactly are we looking at, and where in the car does it go?

I am wiring a reverse camera in and I want to hide the wires,hence my question. 2013 Dynamic Santorini black
2011 XS Lago grey
2007 HLS Stornoway grey
sometimes towing an Elldis AVANTE 574.

Yep, I got that, but what's stopping you concealing them behind a convenient piece of trim, carpet, etc? Where are they that there is no such convenient trim?

I would imagine the three wires going into the unit do different things ? so I would not cut them and join them together.

Iain

Looking at that I'd expect the yellow to be composite video and the red and white to be left and right channel audio.

I suspect ( from experience ) that you only need the yellow for video, both red and white, if following industry standards, are for audio. - unless they are being cheek and using it for power
these cables can be cut to extend them, however note, from my experience, often the inner cable is a mixture of
conductive metal and nylon, so is a real pig to solder.... 

Yes,it appears that the red one is for power. 2013 Dynamic Santorini black
2011 XS Lago grey
2007 HLS Stornoway grey
sometimes towing an Elldis AVANTE 574.

OK, I see the problem. If the white wire is unused you can cut that off - just make sure the cut doesn't squash the wires together and short them out.

The other two you could twist together, but those fine wires can be a pain and not hold together well - a dab of solder will sort that though. (Video quality will suffer if you don't have a good connection, and what constitutes a good enough connection for DC isn't necessarily good enough at video frequencies.) Then you'll need some insulation to keep the wires apart from each other and from any metal part of the car.

If you really can't find any way of concealing the connectors this should work OK, but pcheaven is right - these cables can be a pain to work with!

It is delicate work! I have cut the white wire off and hidden it. Apart from about three inches on show,the
rest is completely hidden. Quite an easy exercise really!  2013 Dynamic Santorini black
2011 XS Lago grey
2007 HLS Stornoway grey
sometimes towing an Elldis AVANTE 574.

if you do cut the wire, you will find one core wrapped around another and as mentioned earlier, the cable is extremely fine.

In my experience of making cuts to re-join cable like this, I find it advantageous to strip back more insulation than you think is necessary, then when it comes to re-assembly do it thus.

You need three pieces of heat shrink tubing, starting with something small to take the smallest core, the idea is to layer a sleeve over a sleeve so replicating the original construction of the cable. This method does make for a stiff section of cable, but it will last.

Cut them staggered along the wire a centimetre or so (1/2") for each addition wire. Before joining the ends, feed a bit of heatshrink over each wire, a nice tight diameter to keep overall size down. Plus a larger piece of heatshrink over the overall wire, a nice fairly tight size.

Don't twist the wires, overlap them end to end & solder (have the soldering iron set up with a fresh bit of solder on the tip so you can hold the wires in each hand (when pushing the wires into each other end to end, very slightly untwisting them with each hand as you feed the ends together helps the wires overlap easier, then re-twist a touch)). Less stress on the wire. It also has the added benefit of keeping the overall diameter with the heatshrink down to a minimum. The finished result should look nice & professional.

Also have the solder wire set up so you can push the solder onto the join with the third or forth finger to add a bit more if needed without letting go of the two wires.

Use the better quality heatshrink, not the cheap rubbish from curtain countries. & just a reminder use the smallest sizes to start with as, as it shrinks it gets proportional thicker. Procrastination, mankind's greatest labour saving device!

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