Trailer Wiring Harness Installation

Range Rover Mark III/L322

Introduction
Factory Wiring Harness Details
Removing the Loadspace Trim Panels
Routing & Securing the Wiring Harness
Connections to Rear Fusebox
Reassembly
Parts & Sources
More Information


Photo at Right: 7-Pin Trailer Connector safely installed on author's 2004 Range Rover

Introduction
Land Rover is gradually catching up with its competition in the matter of towing harnesses. For the first time on a new Range Rover model, there is finally a factory wiring harness for the RR III/L322/LM with North American spec 7-pin and 4-pin plugs. It costs about $200, including an ECU and a relay that plugs into the rear fusebox. This page covers the installation of the factory kit, clarifying some of the detaile on which the supplied instructions are ambiguous. If you plan to tow a trailer heavy enough to require brakes, additional wiring is still needed -- see the RRIII Trailer Brake Control Wiring page. 


Factory Wiring Harness Details
The NAS factory trailer wiring package (see photo at right courtesy of Atlantic British, which is the cheapest source I found and has it for $189) for 2003-05 model years is part number YWJ500012. (The corresponding part for 2006 & up models is YWJ500480). It consists of the following:

• A wire harness with a 7 pin Euro trailer connector at one end and various terminals and multiplugs at the other;

• A Ford-branded adapter that translates the Euro plug into the North American spec 7 pin connector;

• A trailer ECU that installs in the rear fusebox areand controls the various signals to the trailer;

• A relay that needs to be plugged into the rear fusebox;

• Miscellaneous fixings.

An alternative part number is YWJ500012K ($199 at Atlantic British) which includes an adapter for converting the round 7-pin receptacle to the flat 4-pin plug commonly used for light utility trailers. They can also supply the adapter separately, as part number VSA500020ABP, for $17.95.

The harness comes with a fairly good instruction pamphlet, but due to its exclusive use of cartoon pictures with no words (in an effort to make it international) there are some points which are not so clear. The description below is based on my own experience installing the kit, which along with the use of real photos instead of cartoons might clarify some of these points.

Kit for 2006 and up models: The wiring kit for the Jag-engined 2006 & up Range Rover is almost identical but not quite; it goes under a separate part number YWJ500012. It costs about $240. The photo at right shows this kit (couresy of Atlantic British). The details that follow show the procedure on my 2004 model, but the installation of the later model kit should be very similar.


Removing the Loadspace Trim Panels
The trailer harness enters the loadspace through a pre-cut hole in the bodywork, runs along the rear of the spare tire compartment, and makes various connections to the rear fusebox panel, located behind te right rear loadspace trim panels. It is easiest to start by removing all the necessary panels for access. First, the floor panel covering the spare tire is lifted to its fully up position, and can then be easily lifted out. Similarly, the panel covering the storage compartment under the right rear of the loadspace can be hinged up and lifted out, then the vertical panel immediately to its right can be pulled out by pulling on the black plastic handle at its top (photo below left). The molded black plastic liner of the previously mentioned storage compartment can now be lifted out vertically.

Next, the carpeted trim piece lining the right rear of the loadspace against the tailgate is removed (photo above right). This entails unscrewing the right rear chromed loadspace tie-down with an Allen wrench, and removing the two plastic load retainers located on the panel by twisting them 90 degrees counterclockwise and pulling them out. Pulling off the rubber seal around the right section of the tailgate also helps in getting this panel out.

At this point it is convenient to remove the spare tire -- if you are fortunate enough not to have done this before it is a most ingenious process. Unscrew its center fastener, close the lower tailgate, and hook into its top the plastic handle (atttached to the webbed nylon ribbons that pass underneath the tire). Lower the tailgate and "Presto" -- the tire is magically levitated up from its resting place. Stick the supplied plastic brace in the tailgate latch to hold it in place, and you can effortlessly slide the tire out.

Finally it is necessary to remove the entire molded plastic molding that supports the tool kit and serves as a mount for the right lower storage compartment liner. The front section of this molding is underneath the carpeted vertical loadspace trim panel immediately forward of it, so to get it out you have to pry out the plastic stud that holds the bottom of that panel down to the floor (see photo below left), and remove the plastic load retainer on the rear vertical edge of the panel (same as above -- just twist 90 degrees and pull out). This loosens the trim panel enough to get the plastic floor molding out with a bit of difficulty, after undoing its fastenings. The three recessed plastic nuts holding it to the floor are fairly obvious, but it is not clear from the instructions that there are also two plastic clips holding its outer edge to the lower bodywork. These are released  by pulling vigorously up on the outer edge of the modling (photo below left). Now you can get this molding out of the way with a bit of jiggling.

You now have all the access you need to install the wiring harness.


Routing and Securing the Wiring Harness
Here is a point on which I found the instructions a bit vague -- get underneath the rear of your vehicle and peer up in front of the bumper. You will see a rectangular rubber bung sealing a hole in the bodywork, about 18 inches to the left of the hitch receiver (photo below left). Pull off the rubber seal and poke the  trailer wiring harness through it into the spare wheel well so the trailer plug ends up outside the hole. The replacement rubber seal that surrounds the harness can be re-inserted into the rectangular hole.

From inside the spare tire compartment, you can now route the harness's main bundle of wires to the right against its rear wall, in the direction of the rear fusebox (photo above right).  The two loose white wires with ring lugs on their ends are grounded to the body a bit to the left of the entry point (see photo below left).  

Connections to Rear Fusebox
The supplied trailer ECU has to be mounted to the rear fusebox as shown in the pictures below. The white connector needs to be moved out of the way to access the fastenings for the ECU; the instructions do not tell you how to do this so I ended up skinning my knuckles. The photos below show how it is attached and how to dismount it without exerting brute force like I did.

After mounting the ECU, the two multiplugs at the end of the harness can be connected -- the black one to the top of the ECU and the white one to the white plug mentioned above, which can then be restored to its mounted position (photo below left). Then, you can insert the new relay supplied in the kit into the empty spot at top left of the relay cluster (photo below right), and replace Fuse 1 with a 30 amp fuse (not supplied).

In the photo above left, note the blue wire dangling in the breeze at top right; this is simply referre to in the instructions as "unused". It actually comes from the brake terminal on the trailer plug, but no provision is made for its termination. It would be an easy matter for Land Rover to provide for it to be connected to the main wiring harness and emerge in the vicinity of the driver's feet so an aftermarket trailer brake controller could be simply plugged in like it can be for Chevy, Ford, Dodge, Toyota and Nissan trucks and SUVs. As thing stand, however, you have to wire up a brake controller to this blue wire manually -- this problem is dealt with in detail on the RRIII Trailer Brake Control Wiring page.

The next step is to add the red wire from the trailer harness to the white connector immediately above the relay cluster. First remove the connector (squeeze its top and bottom to release its catch).  The wire has a metal tab on the end to clip into the plug -- the photo below left shows the correct hole into which to insert it (not clear in the instructions). I found it required massive force with a pair of pliers to insert the wire before it clips into place -- don't be afraid to push it hard!

We are now done with the wiring, unless you are towing a trailer that has brakes -- in this case you need to run the "unused" blue wire referred to above forward to the vcicinity of the driver's feet. This and other details of brake controller installation are dealt with separately on the RRIII Trailer Brake Control Wiring page.


Reassembly
The panels and moldings you removed for access now have to be reinstalled. This is straightforward except for a couple of items dealt with in the photos below.

If you are just towing a light utility trailer without brakes, your wiring job is complete and you can use the 7-pin to 4-pin adapter supplied in the kit. If you are towing something heavier, trailer brakes are needed. See the RRIII Trailer Brake Control Wiring page.


Parts Sources
Atlantic British -- has low prices on two versions of the factory wiring kit with and without the 4-pin adapter. They also sell the adapter separately.
The Rover Connection -- low prices on all genuine parts including the trailer wiring kit.

More Information
Setting up a RR III for Towing
RRIII Trailer Brake Control Wiring page
Dash Trim Panel Removal Page (RR III/L322).