23-10-2019, 02:41 PM
(This post was last modified: 23-10-2019, 02:51 PM by Zen_Speedmaster.)
I have just finished wiring up the towbar on my 2015 Berlingo van. The van did not come with trailer prep. This means it did not have the loom running to behind the rear passenger side trim panel. This meant that I needed to use a bypass relay. At first I thought this was a curse but, in actual fact I think it was a blessing as I have read several different guides on how to wire up the towbar using the factory loom and it seems like a pain in the towballs!
I bought the kit (towbar and wiring) on ebay for around €165 which I thought was good value. Here is the link
I attached the bypass relay to the van behind the passenger side rear trim cover next to the parking sensors module using a couple of self tappers as shown in the first photo attached.
The relay comes with 2 cables. One that runs from the relay to the towbar plug and the other that goes between the relay and where you tap into the van's lighting wiring. I tapped into the van's lighting wires a few inches in from the plug in the passenger side light cluster. I used the multimeter to determine which wires powered what and the colours are as follows:
Pink (top) = Left indicator
White = Brake lights
Grey = Side light
Yellow+Green = Earth
Green = Fog light
Yellow = Reverse light
Purple (driver's side) = Right indicator
* The purple wire, which is the top wire in the light cluster plug on the driver's side, is for the right indicator. I fished this wire across using the channel over the rear doors.
I removed about 5mm of insulation from each wire and soldered on the appropriate wires going to the relay. The relay came with instructions showing which colours mean what. The colours of the van's lighting wiring do not match the colours of the wiring that came with the relay kit. When I had soldered the joints I covered them in hot glue and wrapped tape outside that.
The bypass relay needs a permanent 12v live feed and an earth. These are the red and white wires at the top of the relay in the picture. There is a very handy earthing point near the rear door where all the other lights are earthed. I used one of the supplied crimp-on rings to attach to this.
The 12v live was another story. After many hours of research I found that there is a plug in the fuse box (glove box) that is there to supply power to the trailer wiring. If the van had come with trailer prep it would have been plugged into this. This is a black plug with a little blue ring at the bottom and a fairly heavy white wire running into it. It is visible through the fuse box door although I did take off the whole glove box assembly for ease of access. This was fairly straightforward and just required me to remove 10 or 12 screws and a couple of push type panel locks. There is a picture of this plug attached. I ran the supplied red wire from the bypass relay up to the glove box fuse box. I had to take off a couple of pieces of trim and manipulate the carpet but it was very simple to do.
This plug did not have any power when I found it first but reading through the threads on this forum taught me how to solve that. In order to get power to this plug I simply had to insert a fuse in the fuse box under the bonnet. This is the same box that contains the ECU. It is not immediately obvious where this fuse should go as the place where it needs to be inserted is hidden. To find the hidden row of fuses I just had to lift up the fuse tray. It is held in place by a couple of clips. When it is lifted up I could see a row of maxi fuses. I had to put a 40A maxi fuse into slot 2 which is the second from the left. With this done I had permanent power to the aforementioned plug in the glove box fuse box. There is a picture of the hidden row of maxi fuses attached.
I do not have the male plug that plugs into this female plug so I attached the power wire for my bypass relay using a female spade connector. The standard sized spade connector I had was actually too small to fit over the quite large male spade connector inside the plug but I was able to widen it sufficiently with a pliers to get a good solid connection. When I ran the red power wire that was supplied with the trailer wiring kit up to the fuse box there was quite a bit of excess. I have left this in place for now as I will be trying to source the correct plug to connect to the plug in the fuse box properly. There is a picture of my semi-temporary connection attached.
I hope this post helps somebody to set up their trailer plug.
2015 Berlingo Enterprise 1.6 HDi