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DBranch, ASE Certified Technician
Category: Car
Satisfied Customers: 706
Experience:  Factory trained Silver Certified Land Rover Technician. 7 years of automotive experience.
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Land Rover..that work on the Trailer when it..flasher..running lights

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I have a 2005 Land Rover LR3-problems with the Trailer lights. Only lights that work on the Trailer when it is connected to the truck are the left side turn, flasher, brake. Right hand lights and running lights on both sides have never worked.

Truck has a Land Rover Trailer Wiring Harness. I'm told that the modulator may be bad but there is not one to be found. It is supposed to be in the back left access panel where the harness is but it is not. I did find 2 relays back there and changed them both but still no luck.

According to Manual, hook up a trailer and put on the blinker the flasher light will show on the instrument panel along with the flashing trailer light. Odd thing is that the left side on the trailer works but the trailer light does not illuminate. Put right blinker on, hooked up to a trailer or not, both flasher and trailer light flash.

Fuses are good but #14 has blown several times while checking circuits. No headlight or right turn power to harness. PLEASE HELP

Welcome to JA.


Does the fuse blow with it hooked to the trailer or without it hooked to the trailer?

Customer: replied 7 years ago.
Can't say for sure, it's happened several times and it may or may not have been hooked to the trailer. The trailer wiring I know is fine because it works with another truck.

Fuse 14 is for the trailer side lamps so you either have a shorted wire on the trailer or in the vehicle. Check over your trailer to see if you see any chaffed wires shorting to the metal frame or what have you. Check this first since it would be easier than checking the car. If you have another trailer you could try hooking up that one to see if the fuse still blows. If not shorts found remove the left rear talight. Has 2 phillips screws and just pulls off. Take a flash light on look down in between the bumper and the body and you will see the trailer wiring coming up form underneath the car. See if you see it rubbing on the body chaffing the wires. If nothing there lower and remove the spare tire you will see the harness running along the top of the frame at the rear of the car check for more shorts on the harness all the way to the trailer plug. If you have a short blowing the fuse more than likely it will be in the area I told you to check. Land Rover has no diagrams for the trailer wiring so it is a pretty much figure it out yourself thing as far as they are concerned. If you dont find anything with the shorts I would replace the trailer wiring. There is no control module on this vehicle for the trailer towing. It is controlled by the central junction box.

Customer: replied 7 years ago.
I'm pretty sure the trailer is fine but will check it again with another vehicle. I still don't understand why there is no power from the front of the truck to the wiring harness except for the left turn signal. There is NO power going to the right turn signal wire or the headlight wire. Doesn't that suggest a problem from the fuse box back to the harness? Also don't understand why the Trailer blinking light comes on on the side (right) that doesn't work but doesn't come on on the side that does work (left)?

If you are not getting power to the harness then yes your problem would be within the car harness. The only thing that you could do is trace the wires in the car you have to have a chaff or the whole harness is cut somewhere. I just looked one more time and they dont have a wiring diagram for the trailer wiring. Wish I could supply you with more info but that is all I can get since Land Rover doesnt ahve it.

Where did you check the harness for power at? On the trailer plug?
Customer: replied 7 years ago.
Checked for power at the wiring harness inside the truck on the input and the output sides of the harness (in the left hand access panel) and at the trailer plug. Power only to the left hand blinker on both the harness and the trailer plug.

That is where it is best to check in the inside. The only other thing I can tell you is to trace the wires back because LR does not supply and connector info or anything about the trailer wiring. You will just have to trace them back to the central junction box which is the fuse box/bcu. If you want me to opt out to see if someone else can help you I will since I dont have anymore info to give you and neither does LR.

Customer: replied 7 years ago.
Can you tell me where to start in the front (and then work back)? Would I need to start behind the fuse box and if so is there easy access? Because there is a problem with both the right blinker power and the headlight (or running lights) power can these wires be crossed and shorting each other out or is it 2 separate problems?

It might be 2 seperate problems unless it is all inside of the junction box. If everything shorted together inside of it then it would cause this. There is no real easy way to get the connectors unlatched on the back of the CJB but drop down the glove box and remove the lower panel underneath the glove box it has 2 screws turn half turn to take and and disconnect the light from the panel. Removing this will give you room to look up from the bottom of the CJB. Is the floor wet on the passenger side or have you ever had a problem with a water leak if so along the entry guard on the passenger side there is a harness and when it gets wet the splices in there corrode and break. Pull up entry guard on right front just clips in just move it out of the way. Then you will see another black plastic cover with 2 white clips in it. the cover goes up underneath the carpet and a little underneath the seat. Pop those 2 clips up with a screwdriver to gain access to the harness. It takes a little effort to move this cover out of the way you can just bent it over to have room. The bulk harness will be in the channel that runs beside the entry guard cut the tape on the harness and check all the the splices they will be wrapped in blue tape and you might have to dig for them. Give them a tug to make sure they dont break and if they do repair them with butt connectors. Not sure if any of these splices are for the lights but I do know there is one in there for the keyless entry rf reciever and one for the power windows but there are a few more and if you have had a water leak they could be damaged so you could chek that also.

Customer: replied 7 years ago.
I have never had a water leak so is it worth my while to check the harness on the passenger side or just check the fuse box?
I would just to be sure it is not real hard to gain access to it but it might be if you have never done it before. This water leak comes form water leaking into the pollen filter then down into the carpet a quick way to tell if you have a leak is to look at the windshield cowl which is the plastic cover that goes across the whole bottom of the windshield where the wipers stick out of. Look at where it meets the windshield you will see a ruuber strip going across the lower part of the windshield. If it doesnt fit flush againist the windshield on the passenger side and there is a gap between the cowl and the windshield that is where your leak is coming from. It then enter into your fresh air intake where your pollen filter is. If you dont see this then I wouldnt worry about it unless you want to check it. I just know that this is a known problem with wiring.
Customer: replied 7 years ago.
If you don't have any other directions I guess we're done here. I didn't think this would be an easy answer but I do appreciate all the time you put into the problem. Just answer me back and I'll hit the accept button. If you want to know what the conclusion to the problem is leave me an email address and I'll let you know how it turns out or let me know if I can contact you at this site.