Trailer Hitch Cable Harness + Module??

[sbradley07]

I have a 2006 XC70 and have read many posts here on installing my own trailer hitch. I'm going with the Class II Hidden Hitch, and didn't want to get into any messy wiring, so I want to get the Volvo wiring harness.

The other posts I read all seem to have been for pre-2006 Volvos where the pn 8698079 was all that was required to do the wiring. But when I look at autowebaccessories.com, it lists the wiring harness (pn 30664651 for 2005+ Volvos) AND something called a Hitch Module (pn 30664974). Does anyone know what this Module is and if I really need it?

Has anyone else tried this on a 2005+ models? Is wiring with the Volvo wiring harness plug-and-play like it is on the pre-05 models? Thanks.

[TrueBlue]

Please bear in mind that I'm in the UK and for folks stateside the exact components will be different, but I feel sure the logic will be the same.

In the UK I bought:-


A detachable tow hitch
Tow bar wiring
Trailer moduleSo the answer to your basic question is "Yes". I have no idea what's in the trailer module, but the tow bar wiring has three flying plugs one (at least) goes into the module and one into the "logic panel" (with all the relays and fuses).

The whole thing is most inelegant - unusual for Volvo. It was much simpler before the CANbus was started.

However, both the cable and module come with copious instructions (here, in multitudinous languages) and illustrations. You have to read the booklets several times because they cover S60/V70/XC70 and XC90 models. It's best to cross out the pages and figures not to be used.

A case of read for two hours and fix in 5 minutes!

I'm sure the US version will be much the same.

[tgwillard]

When I had my OEM hitch installed recently, in addition to the harness (30664651-4) they also installed a control unit (30664974-0). The parts manager had ordered this unit, not knowing if my 06 would require it. The service technician said it would.

[geo]

Hi,
trailer module.
I dont know the exact reason for the module, but
sometimes the car brake or rear fog lamps are turned off or down so the front of your trailer is not lit up everytime you brake, or turn on the fog lamps.
There is also mentioned in the handbook somewhere trailer detection as a wiring feature, so maybe powered trailer brakes or other trailer related functions are allowed for.
Plus with the cambus variations in lamp curcuit loading give fault signals to the vehicles main module, maybe the trailer module actually only takes a signal from the car wiring and switches/relays the trailer lights itself so stopping false fault codes.

well there are a few thoughts.
Geo

[10-cc]

You also need to download software to enable the parking lights. So you have to go to the stealer to do it!

[tgwillard]

Now I know why I had the dealer do the installation.

[sbradley07]

Thanks for all the advice! Here's how it turned out:

Hidden Hitch was simple to install...about an hour's work by myself. The wiring harness and module went in relatively easy, but a little tricky routing the wires under the rear sill trim. The harness came with two 25amp fuses to be plugged into the rear fuse panel, but there were two already there. I hooked everything up to my boat trailer and everything works! Even the special dashboard trailer blinkers were flashing when I activated the turn signals. No software upgrades!!

Thanks again.

[nzoliver]

My dealer told me yesterday that my 2002XC does not need any 'box' which is a nice big saving ($300)! The connector on the car is just a bunch of 'spade' type connectors so I could cut it off and use bullet type or try with the spade type.

[sbradley07]

If by "box" you mean the hitch module, then you are right because they are only required on XC model years 2005 and newer. I got the module for around $62 plus shipping, so not sure where the dealer gets $300 (maybe that's including labor?)

[nzoliver]

Hi,

Nope, the dealers here want NZ$300 for the module!!!! Thats about US$180. :eek: Lucky I dont need it![thumbup]

[WRW624]

Hi all. Just installed the OEM 4-pin tow bar wiring (#30664 651-4) and trailer module (#30664 974-0) to my '07 XC 70. All went well but when I connect to trailer or try a test light I get nothing. No running lamps, no flashers, nothing. 25amp fuses were already installed in car and are both intact. I re-checked all connections (including ground) and all are good. Am I missing something? Do I need to do something to activate the trailer lights or some sort of software upgrade? Any advice would be much appreciated. Needless to say this was frustrating conclusion to an otherwise enjoyable project. Thanks, Dave

[Forkster]

If you have an 07 - you need to visit the stealership, I mean dealership, to get them to activate it. You're not missing anything. An independant shop with a VIDA subscription might be able to do it too.