trailer wiring

[realslimshady]

fitted the towbar to my 2010 xc70, now got to wire it.
Is there an easily accessible way into the loom in the spare wheel well, and if so does anyone know which colour wires are which, and their location?
Any help here appreciated.

[Jms153]

In my experience with Volvo’s the easiest way is to buy a dedicated wiring kit which is virtually plug and play as almost all Volvo’s come pre wired
You should be able to locate the plugs taped up to the wiring loom some where in the boot area
Others on here will have experience of the xc 70

[Tannaton]

You can't just cut into the loom like the old days with scotch locks - you will need at least a bypass relay but preferably the Volvo Trailer module. There's a kit with the module & wiring for around £130 but you will also need software update.

If you splice into the existing loom you will get a number of errors from the bulb failure warning system and it might turn off certain lamps due to overcurrent - brake lamps being the usual one.

[Clan]

Originally Posted by realslimshady

fitted the towbar to my 2010 xc70, now got to wire it.
Is there an easily accessible way into the loom in the spare wheel well, and if so does anyone know which colour wires are which, and their location?
Any help here appreciated.

everything you need to know including instructions ... 13 pin sockets are standard now

https://accessories.volvocars.com/en...CC-480821/2010

[apersson850]

Yes, that's how to do it.
In these cars, there is no pre-wired cabling at all for the trailer. Instead, there's a way to connect a TRailer Module, TRM, to the car's network. That TRM will then give you the pre-wired connections for the trailer socket. The only exception is the constant 12 V feed, which is routed separately from the rear electric distribution center.

[realslimshady]

It only cost me £135 for a towbar and wiring harness (complete with module) I'm not paying £130 for a loom! Which, on inspection, does exactly what a scotchlok does and 'splices' into the original wiring harness. I have the indicators and sidelights working on the trailer board now, and have accessed the loom coming down the L/H D pillar-one of those dozen or so cables must be to the brake lights, all I need is someone to tell me which one, so if anyone can help me with that (got a Haynes manual?), just the colour of the brake light wire and I'll be good to go...cheers...

[Tony Rama]

From Haynes it looks like Green/Brown one side and Violet/Brown the other, but the diagram doesn't explain which is which. These are between the Can/Bus module and the lights.

[apersson850]

I'm not sure what a loom is in this context (not being a native English-speaker), but if you plan on connecting directly to the wires that drive the lights on the car, then you haven't understood anything. Several of these are monitored by the car's system, and will either turn off or indicate faults if you add additional load to them.

[realslimshady]

Originally Posted by apersson850

I'm not sure what a loom is in this context (not being a native English-speaker), but if you plan on connecting directly to the wires that drive the lights on the car, then you haven't understood anything. Several of these are monitored by the car's system, and will either turn off or indicate faults if you add additional load to them.

Thank you for your support and understanding. If you had cared to read what I wrote already, you would have seen that the supplier of the towbar and electrics for said item is in fact aware that direct connection is not possible with these cars and so supplies a module which takes this into account.
This module however, needs a signal from somewhere - hence I need to find the brake light wire to effect this. As I have already successfully done with the sidelights and indicators.
I would respectfully suggest that it is you who hasn't understood the situation.

[realslimshady]

Originally Posted by Tony Rama

From Haynes it looks like Green/Brown one side and Violet/Brown the other, but the diagram doesn't explain which is which. These are between the Can/Bus module and the lights.

Yeah, violet/brown is the wire to the actual bulb, that works. Unfortunately I can't find a violet/brown in the loom. I'm assuming that the loom in the L/H corner of the hatch area is the one coming down from the hatchback, so the wires (both sides the same colour) must change colour somewhere....