Towbar wiring INSTRUCTIONS

[Dave May]

 

Hello Everyone.

This is my first post.

Just purchased a new towbar and electrics on eBay from Towtrust with total cost £212.76. Fitting the bar was no problem. Checked how CANBUS worked and found the brake and tail lights all work on Single filament bulb ( usually a double filament bulb without canbus ). Measured volts on the bulb with tail lights on found 4 volts then measured with foot brake on found 12 volts on same bulb. The universal wiring kit can see the different voltage and light the correct bulbs on my trailer lighting board. This universal wiring kit is JUST FOR 7 PIN TRAILER BOARD not complete caravan kit.

Only had to connect 12v and earth to power the universal RELAY and then only 3 wires to get all lights to work on the board. The Red brake light wire was connected first and both tail lights and the brake light worked, then both direction light wires were connected to finish the job all VERY EASY.

My problem to ask is WHERE TO PERMANENTLY CONNECT THE 12 VOLT SUPPLY TO THE RELAY.  I just jammed a 12v feed into the plug ( red circle on photo) including the 15amp fuse. The instructions say to run a wire directly from the battery to the new relay in the boot. I DO NOT want to do this as the fuse box in the boot has 2 large 12 volt supply cables already. I know I could cut a chunk of insulation from this thick wire and just solder a wire to it but this would not look good and damages car wiring. The boot fuse box should have A TRAILER OUT PLUG but I do not have this.

So has anyone managed to get a 12v feed from this fuse box. The 2 large 12v cables are live all the time even with ignition key removed. I will be fitting an on / off switch so that power to the relay is OFF when not towing. Here are a few photo’s of the rear fusebox.

PS: The FIXED FLANGE towbar DID NOT affect the reversing sensors, they still work perfectly.

Best Regards

Dave

Edited May 4, 2022 by Dave May

[Dave May]

Tried a number of Vauxhall dealers for supply of a TRAILER OUTPUT PLUG so that the 12 supply could be connected to the tow bar universal relay, but nobody in Vauxhall had ever seen this plug and had NO IDEA where to pick up 12volts. 
I then decided carry out the usual method of cutting a chunk of insulation from the 12 volt wire to the rear fuse box and soldering on a wire ( see photo ). The 12 volt supply wire is very thick and to do a good solder joint the soldering iron must be very hot, I used a 48 watt iron which was just right for soldering to this thick wire.
Also spoke to the designer of the universal relay, he told me it is perfectly safe to leave the relay permanently connected to 12volts. I was going to fit a switch to switch off the 12 volts when not towing but now didn’t bother to do that. Tested all working OK.

Edited May 9, 2022 by Dave May

[Vauxhall Owners Club]

Thanks for the very detailed guide to fitting the tow bar electrics.

You seem to have done it very methodically and very neat installation.

 

[Eric2275]

Hi, using your diagram for the electrics on my Insignia Tourer. Everything fine except for the Brown side light wire from the relay. Your diagram doesn’t show where it goes. It appears to be wrapped in black tape and lost..can you enlighten me please or had you just, not connected it when you took the photo..

many thanks

[Dave May]

Hi Eric

I don’t really understand why you think the brown wire is not connected. If you zoom into the relay  ( on photo 2 at the bottom ) you should see the brown wire is connected to pin 5 ( RH side light ), This brown wire is part of the 7 way multi-core that feeds the tow bar electric socket. Note: The PIN numbers are 1-2 -4-5-6-7 pin 3 is not shown.

Dave

 

 

[Eric2275]

Hi Dave sorry it’s taken so long to reply but I have been out of the country.

I can see the brown wire which is part of the seven core and attached to the relay. It was the brown wire on the opposite side of therelai I couldn’t see where it ended up.

[Dave May]

Hi Eric

Cars that have CANBUS wiring DO NOT need to connect the LH tail and RH tail wires ( that’s Black and Brown wires ) to the INPUT of the universal relay.  The Red brake wire is all that is needed to connect to the input of the relay to get the brake and both tail lights to work on the trailer board.

Just connect 12volts and earth to power the universal relay. Then just connect the red brake light to the relay Input. 

Then check the trailer board by just switching on the lights, both side lights will work, then press the brake pedal and see the red brake lights working and the side lights will still be on.

Best Regards

Dave

 

 

[Nickita]

Can someone help?

I would like to know if the CANBUS is damaged. Can that interrupt the functioning of the car? My car won't start. Lack of communication between ECU and BCM.

[Dave May]

Easiest way to see if CANBUS is working is to turn on the lights and check the rear lights. If back lights are working get someone to press the brake pedal and check red brake lights work. You will see  the two side lights just get much brighter ( single filament bulbs ). This is with ignition ON and any trailer board disconnected. 
If CANBUS is not working I don’t think the engine would start. The Haynes manual has good circuit diagrams and fuse locations. 
Dave

 

 

 

 

Edited April 30, 2023 by Dave May