The harness does interact with the suspension. Just get the LR harness, plug and play, and be done with it. They have them at rover connection for 150 bucks.
Land Rover LR3 Genuine OEM Factory Trailer Tow Wiring Harness

 

go with oem

 

Bah that's not what I wanted to hear either...
I also got an lr3 hitch receiver and have been surfing for info on wiring the boat trailer up...

slim pickins!!

I saw on one of the many LR forums that someone spent 12 bucks at an auto parts store and wired it up.. which I'm sure is very possible if you've got some tools, testers and experience doing this.

I was hoping it was as easy as tapping into the wires behind the drivers side taillight and running a standard 5 pole plug for the trailer...

ugh.

 

All this suspension talk scared me from trying my generic unit. So I bought an *authentic new unit for $119 US (TRAILER WIRING KIT | Land Rover Electrical Parts, Batteries, Relays, Lamps & More). It is not oem lr, but they make them 100% identical to the oem and say that they are even better due to thicker wire gauge and better built. Basically same except it does not have the LR logo on the flip cover. The cheapest oem kit I found was $150US - the LR logo is not worth $30 to me.

Still sucks cause the generic kit I have was $30. And it too looks exact like the oem (without the logo) except I would have to hard wire. I'm pritty good with electronics so I am confident that I would have wired it right, but being that the harness ties in with the suspension, I just didn't want to take a chance.

 

Which generic harness did you get? Mind providing info so I can purchase one? I'm going to take a stab at the wiring and I'll document it for the group.

 

The generic unit I bought was from a discount chain store in Canada called Princess Auto. Not sure if they are in the US too? Though this generic harness basically had the 4-prong connector on the back with 4 extra wires for the charging for the circular prong - these 3 wires where red, black, blue. I'm sure any hardware store would sell similar. The trick is wiring these to the LR3 - it really would not be that difficult except for the talk that someone LR tied the air suspension into the same wiring intyended for the tow harness?

 

I think it also interacts with rear PDC if you have that, not sure if that's a big deal.

 

I wired up my 2008 LR3 trailer with less than $20 in parts from AutoZone

So after reading the instructions at Land Rover LR3 Discovery 3 for the generic harness they sell - I decided to take a stab at wiring the trailer myself with some over the counter parts.
I saw from the pictures there were 6 wires clearly visible from the 2 harnesses... I didn't think it could be too difficult.

I bought a 10 dollar 7pole RV trailer adapter that fits in the stock space perfectly after hacking the rear 1" off. The length of the adapter was too long and was rubbing on the spare tire so I took an inch off and its fits fine, and lines up with all 4 screw holes on the front end. My trailer is a 5 way flat and I already had the 7 to 5 way adapter.

I also bought a 2 dollar wire tester that lights up.
I used this to identify the left, right, parking, and reverse lamps.
My boat trailer has a 5 way flat plug so I knew I only needed those 4, plus the ground. I used a ground bolt that was conveniently located right in the compartment with the 2 plugs.

I chopped the stock harness plugs off and used twist wire nuts to connect the wires. It was a little too tight in there to fit wire taps so I wanted to have good clean connections and decided I could do without the harnesses.
There are 3 wires in each of the stock harnesses. One of them is a very thick orange wire that tested always on with the key ignition in the on postion. I think this may have been the aux power - my trailer does not use that so I did not wire it to the 7way wire harness. You can easily identify the lights with the wire tester:
Yellow: left blinker
Green: right blinker
Brown: tail lights
Green/Brown stripe: reverse lights
The instructions in the link above provided all the info I need about running through the grommets etc. I used a metal hanger to snake the wire through the bumper to the connection area from below the tail light.

The 10 dollar 7way harness also had a good diagram showing which wire went to which location on it.

I used 14 guage wire which appears to be the same as the OEM.

Very easy and well worth the savings!
Works like a charm!

 

Why even consider a generic harness? A $50k truck and you dont wanna spend the extra 100 bucks to get the right electronics? Id say go OEM

 

I guess that's the difference between me and a lot of other people on the board here..
I'm an engineer and I enjoy figuring things out.
Who in their right mind would spend 150 bucks on a few pieces of wire that do the same exact job as 15 dollars of wire from a local auto store..

Buying the 150 wires makes no sense to me and is much less enjoyable to install because there's no engineering involved.

To each's own
I'd rather save 100 bucks and buy a nice bottle of wine.

 

There are a number of reasons people would spend the $150. Easy, clean, and LR approved.

That's great if it works for you though foozed. With your setup, does the dash indicate you have a trailer hooked up?

 

Yep, get the little blinker icon on the dash when blinking etc. I'm sure that's activated from the voltage draw on those lines since they are specific to the trailer.

 

There should be a little trailer icon lit up. Tow mode if you will.

 

It comes on when you use your blinkers. It is not on constantly.
IT dose not work with LED trailer lights. and the LEDs will flash lightly but constantly.

 

I also did this mod. Massive money savings. Dealer in Canada was over $200. Shipping from the US wouldn't get it here in time for when I need it ready.

I've got my 4 Pole Plug all wired up. No issues there, all I need to do what I need to do.

My LR3 is an 05 SE. I noticed that the Two Plugs in compartment on mine have a total of 7 Circuits rather than 6. Anyone know what the 7th one is for?

Green = Right Turn Lamp
Yellow = Left Turn Lamp
Brown = Tail Lamps
Blue = Brake Controller
Dark Green/Brown = Reverse
Orange = Aux Power Supply
Red/Yellow = ????? This one didn't show any voltage during the normal Left/Right/Brakes/Reverse routine. I have a separate Ground Wire from the actual plug to the Chassis, so I don't think its a ground.

Anyone?

 

Turns out it is for Rear Fog Lights.

Green = Right Turn Lamp
Yellow = Left Turn Lamp
Brown = Tail Lamps
Blue = Brake Controller
Dark Green/Brown = Reverse
Orange = Aux Power Supply
Red/Yellow = Rear Fog Lights

So, there you have it for an 05 LR3.

BTW, the whole thing took about an hour, total cost $40 CAD. I never had to cut the Factory Harness either. Was able to find an assortment of Solderless crimp connectors that plugged into the circuits just fine.

FWIW, I cannot see any evidence that this wiring interacts with Suspension at all. No fears there.

Scotty

 

Really happy I came across this thread. I am going to be doing this here in the next week. The OEM trailer wiring harness is exactly what drives me crazy about Land Rover. There's no reason for this to cost $200, not to mention it didn't just come installed with the "tow package" which seems insane. Wish me luck.