Tow Bar Wiring without special harness
 

Hi All,

Apologies if this is a avaliable in the search but it doesn't seem to work on my phone.

I've just fitted a witter tow bar but I didn't realise, as is with everything Volvo, they have their own special kits for wiring up the harness.

Am I good to just splice the wires in as usual with a DIY fit or do I really need this kit? At nearly £100 I would rather not. I'm also away camping as of Monday and we need the tow bar sorted.

If I'm good to splice in then does anyone have any diagrams or know of any good youtube vids to look at?

Any help is greatly appreciated :-)

Please do not splice into the wiring. You will cost yourself thousands of pounds in repairs. Do it right do it once. Take it on the chin and relax that it has been done right.

Hi Kenny,

Thanks for the reply.

Could you elaborate further please? Are there systems on the Volvo that I would be bypassing or tripping by not using their harness? I've done it a couple of times on other vehicles and its not been an issue so just wonder what's different.

I've just found a guy on youtube from etrailer.com who has spliced into the wiring and it wasnt an issue.

Like I said, not ignoring your advice, it just helps to have something to explain to the Mrs when I explain that we are shelling out another £100 that's all :-D

Found the video....

https://youtu.be/HUzzuKufLS8

Don't use a universal wiring kit. Use the Volvo kit every time. They are about the same price, even cheaper sometimes and will just work.

Volvo spent millions designing you a great car with lots of Goodies like abs traction control. They went on to design a trailer module and wiring system that lets the car know when you have a trailer attached. When towing this system talks with the car and changes the way it brakes the way the traction control works when the gears change if you have an auto and alters throttle control etc. Your £100 gets you a lot more than just making the trailer lights work. Splicing wires stops all theses safety systems working and can overload lighting modules.

How old is your XC90?
Mine is 2003 and the official wiring loom is simply the wires with a plug on the end.
As mine was fitted with 7 pin and I needed 13, I cut the plug off and soldered to the tails. No problems.
I did the same on my 2003 V70 (same loom), again, no problems.

You will need to add two relays and two fuses. There is a diagram somewhere showing which to add.

The only issue doing it this way is that the fog light over-ride doesn't work, this needs to be programmed by a dealer. Basically, when your trailer is plugged in, it will turn off the car's rear fog lamp so you don't get reflected glare.

I'm a fan of the Volvo loom and you can get them for around £40ish on eBay or Amazon BUT depending on the age of the car you can use a universal kit but not splicing into the loom at the lights.

You should find a grey plug in the spare wheel well, this is what the towbar loom plugs into. Either cut off the wires needed form the plug or strip the flex away. Either way solder the joints. Scotch locks are ok but eventually cause poor connections.

The wiring loom plugs into the trailer module at the REM (behind the trim in the rear LH corner).

So I'm getting really confused here....

I have a 2004 53 plate. According to PFJones they only started doing a dedicated loom from May/June 2004, after my vehicle was manufactured. They said all I need is a 7 bypass relay and then I can use the universal kit to fit the electrics in. I have also rung around and there isn't a dedicated loom for my age of vehicle?

This grey plug, where is it? I've found one behind the light cluster on the drivers side but nothing in the wheel well or around the battery.