How to connect trailer cable to existing wires?

Hi,

I am about to install a brand new tow bar on my car using the classic 7-wire system. For that matter it is common to use the popular self stripping connectors and simple enter the wire into one of the rear light cavities and hook it up to all the wires supplying power to the rear lights.

https://www.autoelectricsupplies.co.uk/product/61/category/8

I am truly not a fan of these connectors.

What is the correct and professional way of connecting a trailer wire to the existing automotive wiring system?

Lucas

I'm not a professional.

That being said, for me....is the connection inside the vehicle? Solder and heat shrink. Is it exposed to the elements? Solder and adhesive lined heat shrink, and loom it up.   If you can't solder for whatever reason, crimp with adhesive lined heat shrink crimps.

So you want to tap into an existing wire by removing lets say 10mm of insulation exposing the copper and then solder the trailer wire directly onto that spot?

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1991 Toyota Corolla AE92 Liftback

Well, you would have to cut the wire to get the heat shrink on it.

So what you are saying is: Destroy the existing wire system by cutting it in two and then solder everything together again?

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1991 Toyota Corolla AE92 Liftback

What mscguy says in his first post is the correct answer.
Note many modern Euro cars have a tow plug, check with your dealer/manufacturer.
And you said destroy. We didn't.
It's a common procedure with alarms/remote starts.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

There is often an inline connector in the rear lighting harness in the vicinity of where you might want to do the interface. Particularly on pick ups. Sometimes it is possible to remove the terminal from the connector, put the heat-shrink over it, strip the wire, solder and shrink, then re-insert the terminal back into the connector. Depends on the style of connector, and your patience in de-pinning it.

There are also commercially available coatings for sealing the splice and insulation after you do the strip and attach. Then wrap the connection with self-sealing tape.

If I go with the cut-the-wire-in-two approach, I use heat-shrink butt splices. Particularly if the splices are under the vehicle where they are subject to conditions that promote corrosion.

There are t-harnesses available for hundreds of makes and models. You just unclip your connector at each harness and place the new connector between. They'll usually also come with a unit that converts your car's two wire tail/turn lights to a one wire for trailers.
Also I'm a bit confused on what you'll be doing to supply the brake and 12 volt pins of your 7 way. Don't do that from any wiring you find at the rear of the vehicle.
Also, many of the kits like I mentioned above will only use your existing wiring to trigger a relay, and will actually power your trailer from a fused battery connection. This is the way to go. I do these in my sleep, let me know if you have questions.

https://www.hopkinstowingsolutions.com/

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2000 Subaru OBW Ltd