Dedicated towing harness - Reverse issue

If the instructions say you need to break into the wiring harness then I would suggest you follow this. Sometimes it is just not practical to have a suitable interconnect for all models and derivatives, poor show but if that what they designed then I cant see you having an option.

just buy a couple of scotch locks and crimp into the reverse wire as instructions state. very cheap and quick. job done.  

Looks like you have to do what is recommended, very unfortunate.

Mine has a dedicated CanBus harness and when towing, if reverse is selected the cars reversing lights are inhibited and the caravans turn on. I suppose it stops glare from the front reflection of the caravan but doesn't help that much with the caravans reverse lights so far away, plus reversing in the dark is a very rare occurrence for me and I wouldn't bother.

Although the instructions say to splice in, I would ask the dealer that splicing into the cars harness would not be an excuse to void your warranty (if you have one) if any electrical problems happened one day. So easy to blame that and use it as an excuse.

These Scotchlock connectors are rather brutal and a fault waiting to happen.  I would not use then on a vehicle that I was keeping for more than 24 months, especially if the location they are to be used is damp. The cores of the wires involved are open to atmosphere and the copper will follow the laws of chemistry to become copper oxide.

A decent elecrician would strip a short length of the wire and solder on the new connection, making it all waterproof with self-amalgamating tape. 

I have used scotchlocks in the past and then wrapped in electrical tape. No problem over a couple of cars and 8 to 10 years usage. 

Scotchlocks should be banned ..... they're a bodge. 

I'm a decent electrician and I use scotch locks all the time on auto wiring. I haven't been asked to solder a wire onto a connection for over 30 years, and that was for GPO JB multicore wiring, in fact I don't believe open reach solder joints either now.

Provided you make the connection correctly, use the correct size you will have no issues in my experience.

My NTTA local fitter also uses them.

90% of connections are now crimp connections, but using  those in a car involves cutting the wire to make a connection, not something I would be happy doing, scotch lock are preferred.

Scothlocks are a bodge.

There are no ID (insulation displacement) terminals used in any road vehicle by the OE manufacturers. There is a reason for this, they fail, they corrode, they let moisture into the harness, they are a poor joint with increased resistance in the circuit.

Telephone companies use ID terminals because once they have fitted them they are not subject to vibration. The telephone ones are at least gel filled to stop moisture penetration.

No auto electrician should ever use them, there are many papers written on the many automotive attempts to use ID terminals over the years, most are of the autopsy type on what went wrong.

Cutting the cable, twisting, soldering and insulating is the correct thing to do. If you are not confident enough to DIY then find someone who is.

I would never allow someone to scotchlock a towing harness into my vehicle, I would question their competence.

They are quick and cheap, if that's what you want  then fine.

In your opinions MM and Phising they are a bodge. 

Not my first choice but I have used them in the past without any problems whatsoever. 

Its not true that road side JB don't suffer  from vibration, they do. How many people have had a problem with their phone master socket?  they don't use soldered joints either.

They would be no practical reason for an auto maker to use scotch locks, it would be totally impractical, the plug and socket arrangement using crimped connections is the only sensible way for a quick install.

Cutting a cable and soldering is a dated method which in its self can lead to problems, I would avoid this type of bodge job.

The only time I use a soldering iron is when making up electronic boards as an hobby, and even the incoming wiring to that is via crimp lug connectors.