Trailer Wiring Harness Installation (Range Rover III/L322/LM)

Trailer Wiring Harness Installation (Range Rover III/L3222/LM)

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) is part number YWJ500012. 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.

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.


Lift tab up (bottom arrow) to remove lower panel covering storage compartment. Then, the side panel covering the rear fusebox can be removed by pulling on the black handle (top arrow). Note panel to right (rear) is secured by two plastic lad retainers and a steel one (bottom right of photo).	Closeup of one plastic load retainer. Removal is accomplished by rotating 90 degrees and pulling out.	Top & middle arrows show locations of removed plastic load retainers (closeup at right). Lower arrow shows location of removed steel tie-down. Rubber seal is pulled away from lower tailgate to ease panel removal.

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.

Removing the black plastic molding. Black arrow shows location of removed plastic stud; immediately above it is location of another removed plastic load retainer. The three large diameter holes running diagonally across the middle of the picture are the locations of the recessed plastic nuts retaining the molding. The two white arrows indicate required upward pull on the molding's outer edge to release two hidden plastic clips.

View of right hand side of loadspace interior after removing the spare tire, the trim panels and the black plastic molding.

You now have all the access you need to instal 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.


Looking up and to left under the rear bumper, white arrow points to rectangular hole in body (covered by rubber seal) through which harness is fed. Steel tab below arrowhead is for mounting the trailer plug. Hitch receiver is in right foreground.	Harness threaded through the rectangular hole, with new rubber bung surrounding it. At bottom of photo the trailer connector bracket and plug have been has been attached to the steel tab.

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).


Picture taken from inside the loadspace looking aft. Rigthmost upper arrow shows harness entry point; other upper arrows show its routing across rear of tire compartment to right of vehicle (left of picture). Lower arrow shows terminal where harness's two white wires are grounded.	Continuing the routing of the harness across the rear of the vehicle to the space occupied by the rear fusebox. Arrow shows point where the harness wrapping protects it from sharp metal on the bodywork. Note beyond that the harness is routed upwards alongside the thick existing harness.

Running the main harness bundle across the back of the compartment, there is one plastic clip that secures it in place, but otherwise it fairly naturally falls into place. Where it crosses into the right rear loadspace/fusebox area (arrow in photo below), there is a metal edge sticking up, but the wire bundle is protected at this point by a thick cloth wrapping. From this point the harness is run vertically against the existing wire bundle going up into the rear fusebox compartment.

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.


	Top Left: Rear fusebox. Note white connector (arrow) Top Right: White connector removed for access to mount trailer ECU (white box at center of picture) Far Left: Closeup of flexible tabs on rear of white connector. Gently bending them inward will disengage the plug from the mounting panel (right) so it can be lifted out without skinning your knuckles like I did using the brute force method!

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).


Black multiplug connected to top of trailer ECU, and white multiplug connected to the white connector immediately to its right.	Top arrow shows connector that has to be removed for next step, to insert red wire into it. Middle arrow shows new relay in place Lower arrow shows Fuse1 (20 Amps) that has to be replaced with a 30 amp fuse.

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!


Red wire being inserted into 2nd hole from left in top row of white connector. I spread the tabs inside the plastic connector a bit with a small screwdriver to try and ease the way, but it still needed considerable force.	Harness wiring completed, with diagonal red wire at center affixed to connector above relay cluster. Arrow at top right indicates loose connector on end of "unused" blue wire which is for the trailer brake control connection (see below).

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.


When replacing the plastic molding that holds the tools etc on the right side of the loadspace floor, the plastic nuts are hard to get back on to their deeply recessed bolts. A magnetic socket is no use, but I found a pair of very long nosed pliers helped i getting the nuts into position and the threads started.	The two-part plastic studs that hold the carpeted trim pieces in place come out easily enough, but putting them back in is another mattter. I found that extending them to their full length allowed me to squeeze the ends together enough to get them back into their holes, after which a hard push or a bash with a hammer seated them back into place.

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/LM).

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