Fitting a towbar is usually pretty easy and most people with a little mechanical knowledge, and in this article, I will explain how to fit 7 pin towbar electrics.
With a simple tool kit, you can have a towbar fitted in a couple of hours. However, when it comes to fiddling with vehicle electrics a lot of people run scared as soon as they crack open a wiring diagram.
This is a guide to fitting the standard 7-pin trailer lights hook up to a Ford Transit Mk7 Van.
However, this towbar electrics method will work with any car, van or camper with similar wiring. With a little thought, this will help if you are wiring up a vehicle with more modern wiring.
More modern vehicles use a CANBUS, Car Area Network Bus, system. This means that it uses signal wires to turn the lights on and off using relays, rather than sending the power directly to them from the switch. You need to use a towbar electrics bypass relay to wire into these. As my Ford Transit camper van is old school so I didn’t need to use one of these, however for a relay you simply tap into the signal wires to the relay rather than into the power cables.
If you can afford it you could use the vehicle specific trailer wiring that the manufacturer provides. There should be connections already in the wiring loom to connect it. These can be pretty expensive, and it can be a problem finding the connectors in the loom anyway.
You can also use the vehicle towbar wiring diagram to get the wire colours to connect. I was surprised to find a lot of conflicting and different information about the wire colours for a Mk7 Transit. It’s expected that a Transit would be pretty standard over many years, but this doesn’t seem to be the case.
In my experience, I usually find it best to work out the colours of the wires from the connector to the rear light cluster. It is a bit belt and braces but this works with most vehicles.
Towbar Wiring Kit and parts you will need for fitting
- 7 Pin Electric Towbar Wiring Kit: https://ebay.us/Vvw5Us
- 7 Core 0.5mm 11amp cable: https://ebay.us/iiY83F
- Loom Tape: https://ebay.us/7YMbiE
- Solder Sleeve Connectors: https://ebay.us/O2LuVn
- 12v Test Probe: https://ebay.us/zMQFO5
First I remove both light clusters from the rear of the vehicle, but leaving the bulb connectors plugged in. By turning the lights on and off, you can use a 12v test probe to determine which wire is which from the light cluster connector.
This is fairly easy once you get the idea of what you are looking for, and you can manage on your own for most of them apart from the brake light. But even this can be worked out using a process of elimination.
For my Ford Transit mark 7 van. the wires I needed to work it out like this.
Transit Van Right-hand rear light cluster wiring colours
| Wire Colour | Connecting To |
|---|---|
| Red | Foglight |
| Black/Green | Earth |
| Purple/White | Brake Light |
| Yellow/Grey | Tail Light |
| Green/Orange | R/H Indicator |
| Green/Brown | Reverse Light |
Left-hand rear light cluster wires used for towbar electrics
| Wire Colour | Connecting To |
|---|---|
| Blue/Brown | Tail Light |
| Grey/Orange | L/H Indicator |
You also have to wire in an audible beeper that confirms that the tail indicator lights are working.
7-Pin Electrics Towbar Wiring Diagram
Some wires join end to end, with only a few that need joining into a wire that runs to the connector block.
To join wires that are a straight end to end connection I use solder seal sleeves where I could, which I find really good to connect one wire to another. These work really well and are very easy to use, if you have a good lighter or a hot air gun.
I only use Scotch Locks where I have to tap into another wire. I am not that keen on using these, but they do work well. You could strip the insulation and solder the wires on. I always think that I will do this, but end up using Scotch Locks anyway 🙂
Once you have finished you need to check your towbar electrics are is all working. If you have a trailer or a light board you can just plug it in to test that you have got everything wired up correctly. If not you can use the test probe to check that each of the pins in the hookup works correctly. You simply turn on the relevant light and use the 12v test probe to connect it to earth and see if the light comes on.
To conclude, once you have tested that it all works you should cover everything with Loom Tape to stop the wires from straining and to keep everything neat. You need to check the fit of the cluster to make sure it has room for the extra bulk of the additional wiring. Sometimes you have to move things around a little.
Towbar Wiring Guide Video
For those of you who prefer to follow this towbar electrics installation guide in video format, here is our guide video for 7-pin towbar electrics with step by step explanation of the wiring: