The rear fog lights come on when I plug the trailer in

[DDdisco]

Gday all,

I've done a search and couldn't really find a similar problem When I plug the trailer (a horse float) into my Disco 3, the rear fog lights (including the dash indicator) come on. This happens regardless of the light switch or ignition switch position. Everything else works as it should.

Does anyone have any ideas?

Cheers

[bee utey]

Gday all,

I've done a search and couldn't really find a similar problem When I plug the trailer (a horse float) into my Disco 3, the rear fog lights (including the dash indicator) come on. This happens regardless of the light switch or ignition switch position. Everything else works as it should.

Does anyone have any ideas?

Cheers
If I didn't know better I would say your vehicle runs a CAN/BUS system for the rear lights, the wiring for the trailer may be overloading the circuits. The float also may have bridged connectors for running on different sockets. Once you have identified which plug contacts on your D3 are for what lights, you might have to check there are no bridged wires in the float's plug. I have been told the only way to run trailer lights on new cars is to run relays off the relevant rear lamps, and power them from the battery feed up the front.

[DDdisco]

Thanks for the info. The trailer is wired standard with no bridged connectors, but it does have a number of clearance lights etc. Might have to get someone to look at it.

[sniegy]

I would assume you have trailer brakes towing a horse float!
What type of brakes do you run, electric or a brakeaway style?
Can i ask who wired in the trailer brakes? if you have them, Was it a dealer? or a recommended auto electrician?
You need to be careful who wires in the trailer brakes as the wiring needs to be modified not to cause problems.
I think you may have a wiring problem on possibly the vehicle & maybe even the float??

Good luck.

Cheers

[DDdisco]

I've only just bought the vehicle and haven't had the brake controller installed yet. There was no problem on the previous vehicle (a Patrol), and all the lights on the trailer work properly (including the tell-tale on the dash with the indicators).

I'm going to get the controller wired in by the local dealer, but wanted to get to the bottom of this before I add to the complexity of the diagnosis!

[sniegy]

Does the no.2 pin on the trailer need a supply for the battery for the horse float, if it does then this will be back feed to the vehicle suppling power to the fog lights.
HTH

[bee utey]

I've only just bought the vehicle and haven't had the brake controller installed yet. There was no problem on the previous vehicle (a Patrol), and all the lights on the trailer work properly (including the tell-tale on the dash with the indicators).

I'm going to get the controller wired in by the local dealer, but wanted to get to the bottom of this before I add to the complexity of the diagnosis!
I suggest you disconnect each load circuit at the trailer plug one at a time until the fog lamp goes out. Fit a relay to the offending circuit (probably the tail lights) with a battery power feed. Your power feed can be a rear outlet for fridge etc.

[DDdisco]

Thanks for the ideas. I'll check the number 2 pin. The float has got cameras in it that I have never used. Maybe that's a power feed to them. There's no other power feed (other than the lights). Otherwise I guess I'll just check one circuit at a time.

[bee utey]

Thanks for the ideas. I'll check the number 2 pin. The float has got cameras in it that I have never used. Maybe that's a power feed to them. There's no other power feed (other than the lights). Otherwise I guess I'll just check one circuit at a time.

Sorry I meant a power feed to a new relay inside the car, to prevent the trailer load coming directly off the lamp circuit.

It means the relay puts only an extra 0.2 amp load to the car's light circuit, and all the extra lamps' amps are handled by the relay using power from the car battery, via a new or existing power feed wire to the back.

[DDdisco]

No worries. Thanks!

[Nomad9]

Hi DDdisco,
Funny you should mention this, I've installed a Tekonsha Prodigy brake controller in my 2005 D3, I ran the blue wire from the brake controller right back to the trailer wiring connection behind the nearside rear bumper under the light cluster. I wired everything up making sure everything was right, made sure I didn't do the mirror image wiring trick where you wire things up the mirror image that you are supposed to do. I checked the wiring for the trailer, the whole deal.
Despite all this the trailer brakes wouldn't work. I've given up now trying to figure out whats going on, the blue wire behind the bumper comes out as the black wire connection in the trailer plug. For me it was easier to change the wiring on the camper trailer to suit. Everything works fine now all the other wiring worked a treat with no changes. Got me buggered this one, I even wired up a separate long lead to connect the trailer to the vehicle in the shed (a suggestion from someone on this forum), this made things a lot easier than trying to get the camper near enough to the vehicle to try things out.
Wiring things up to the connector at the back behind the bumper bar was the way to go, saves making a mess of the can bus system like I did first time round. It's a pain in the butt running wires the full length of the vehicle but this I've found personally to be the safest way to do this. Hope this helps.

[DDdisco]

Thanks Nomad9,

I want to try to keep the wiring on the trailer as standard as I can (just in case I have to tow it with another vehicle), rather than wire it to suit the car. I think it's a job for next weekend!

[Tote]

On my 2008 build D3 the wiring is still wired per the UK standard which uses the brake wire as one of the feeds for the clearance lights. This causes the trailer brakes to come on when the park lights are switched on. I believe some dealers cut the wire feeding the second clearance lamp circuit on vehicle delivery, but mine was not done. Do a search on trailer wiring on here and you may get a few more answers.
The Australian trailer wiring scheme allows for the pin on the trailer that supplies power for reversing lights to also provide 12v auxuillary power so that might be something worth checking.
I'd follow sniegy's advice re pin 2 and check what has been wired up to your float on that wire.
I have pulled many different trailers with my D3 and the only problem I have had is the one where the electric brakes come on with the park lights. I use a standard round to flat adapter plug purchased from an auto accessory shop to tow these.
LED Tailights will complicate the issue further as the Disco 3 sends a pulse through the trailer wiring to test for blown bulbs. This will illuminate LED taillights but not incandescant ones and causes an annoying flash on the blinkers. There are boxes you can buy to fix this but it's easier to use normal taillights if you have the choice ( search for pulse shunt )


IMHO you dont need relays to isolate the trailer wiring although this would probably also fix the flashing problem with the blinkers as the relay would not have time to make contact and illuminate the LED blinkers when the pulse is active.

Regards,
Tote

[sniegy]

Hi DDdisco,
Funny you should mention this, I've installed a Tekonsha Prodigy brake controller in my 2005 D3, I ran the blue wire from the brake controller right back to the trailer wiring connection behind the nearside rear bumper under the light cluster. I wired everything up making sure everything was right, made sure I didn't do the mirror image wiring trick where you wire things up the mirror image that you are supposed to do. I checked the wiring for the trailer, the whole deal.
Despite all this the trailer brakes wouldn't work. I've given up now trying to figure out whats going on, the blue wire behind the bumper comes out as the black wire connection in the trailer plug. For me it was easier to change the wiring on the camper trailer to suit. Everything works fine now all the other wiring worked a treat with no changes. Got me buggered this one, I even wired up a separate long lead to connect the trailer to the vehicle in the shed (a suggestion from someone on this forum), this made things a lot easier than trying to get the camper near enough to the vehicle to try things out.
Wiring things up to the connector at the back behind the bumper bar was the way to go, saves making a mess of the can bus system like I did first time round. It's a pain in the butt running wires the full length of the vehicle but this I've found personally to be the safest way to do this. Hope this helps.
Nomad,
Please say someone has cut the 2nd park light circuit wire!
Find the fuse box in the l/h/r section of the vehicle behind the little panel, (also refer d3 wiring trailer brake instructions)push tab back & remove fuse block toward inside of vehicle.
Cut the brown wire an inch or so away & solder the fuse block end to the black wire next to it.
If you dont & you are towing & you travel through a tunnel at 100kmh & the lights are set to auto the brakes in the trailer you are towing will come & your pants will need to be replaced.:p
Any queries dont hesitate to ask.

[Nomad9]

Sniegy,
In all honesty I haven't done this but I will, I did the same mod on my first D3 and didn't have a problem, but I also didn't have auto lights. Muchly appreciated. So the brown wire that is now an inch long gets soldered to the black wire next to it, what happens to the other end of the cut wire? Do I just cap it off and make it safe? Which side of the fuse do I cut the wire, the in coming or the out going wire? Does it matter?

[DDdisco]

Well, the D3 went off to the local dealer yesterday to get them to look at the wiring and fit the brake unit. They where wholly unhelpful and disinterested, and said to take it to the local 4WD place to get them to do it.

[sniegy]

Sniegy,
In all honesty I haven't done this but I will, I did the same mod on my first D3 and didn't have a problem, but I also didn't have auto lights. Muchly appreciated. So the brown wire that is now an inch long gets soldered to the black wire next to it YES, what happens to the other end of the cut wire? This wire now becomes the connection point for the blue wire from your trailer brake controller Do I just cap it off and make it safe? Which side of the fuse do I cut the wire, the in coming or the out going wire? Does it matter?There is only one side that has these colors
Nomad, sorry for the late reply, been very busy.


Well, the D3 went off to the local dealer yesterday to get them to look at the wiring and fit the brake unit. They where wholly unhelpful and disinterested, and said to take it to the local 4WD place to get them to do it.
:eek::eek:. If u need some help doing this ring me 0414 533 085 HTH

[DDdisco]

Just an update. Had the Hayman Reese brake controller fitted, and it works perfectly, except the rear fog lights are still on whenever the trailer is plugged in.

I disconnected the trailer pin 2 wire (still haven't had time to see what it is connected to), and it fixed the problem.

Thanks for all your help. :)

[Dirty3]

Can i ask who wired in the trailer brakes? if you have them, Was it a dealer? or a recommended auto electrician?
You need to be careful who wires in the trailer brakes as the wiring needs to be modified not to cause problems.

Hi Pete,

I have a similar problem here as I just purchased a camper trailer (not LED lights) and went to plug in the trailer and the rear brake lights on the D3 come on. No ignition on. When you mention wiring, who should I take the car/trailer to? Will any auto electrician do, or does it need to be someone who knows Land Rovers? I usually use ULR for all my servicing, but if you can recommend anyone, I'd prefer someone that knows what to look for. Problem is I don't wan tot tow it plugged in or without lights....any idea's. I could try testing the plug, but I'm no electrician.

Cheers Neil.

[LeighW]

Hi DDdisco - when I had my D3 wired for a Tekonsha brake controller the electrician chose to NOT follow my printed instructions (from fellow Aussie on disco3.co.uk site) and I had the same problem with the fog lamps being lit when the trailer was connected. I didn't return vehicle to him as I wasn't too pleased that he hadn't followed specific instructions in the first place. I assume in his mind he was the professional and I was only an interested amatuer.

I solved my problem by removing the globes and am not overly concerned that they are not there as I have not needed them. Your case may be different as I note you are on the Darling Downs and may experiance fog.

My regular dealer has not noted that the fog lamps are not there either; not once in 3.5 years of servicing...

[DDdisco]

Thanks for that. I had the electric brake unit fitted by the place recommended by the dealer, so I'm not sure exactly how it was hooked up, but assume it was done to the LR specs. I followed sniegy's advice and disconnected pin 2 in the trailer plug (not on the vehicle). I still haven't gotten around to finding out what it used to do, but it has cured the problem. The brakes and the fog lights work as they should. I guess one day I'll find out what that wire is connected to!

Cheers

[sniegy]

Hi Pete,

I have a similar problem here as I just purchased a camper trailer (not LED lights) and went to plug in the trailer and the rear brake lights on the D3 come on. No ignition on. When you mention wiring, who should I take the car/trailer to? Will any auto electrician do, or does it need to be someone who knows Land Rovers? I usually use ULR for all my servicing, but if you can recommend anyone, I'd prefer someone that knows what to look for. Problem is I don't wan tot tow it plugged in or without lights....any idea's. I could try testing the plug, but I'm no electrician.

Cheers Neil.

Hi Hedley,
I work for MLR, so the guys over at ULR should know what they are doing.
I would prefer for it to be sent to a dealer as they know the vehicle a little better than the local Auto Elec. The dealer also has a reputation to withhold.
So the work is guaranteed.
Be happy to have a look at it at MLR also if u wish. Let me know if u do.
Cheers.

[Dirty3]

I followed sniegy's advice and disconnected pin 2 in the trailer plug (not on the vehicle). I still haven't gotten around to finding out what it used to do, but it has cured the problem. The brakes and the fog lights work as they should. I guess one day I'll find out what that wire is connected to!

I might also have a look at this as it is quite possible that what I saw were the fog lights and NOT the brake lights. Maybe this is the problem? Also could the std plug on the car be wired incorrect? I pulled it apart on the weekend, but as the wiring loom is so tightly fitted, it's hard to tell what coloured wires go to which pin. I even dropped the spare tyre as it appeared to foul the loom but it was not the case, just neat & tidy wiring.
I'll give ULR a call thanks Pete and go from there, if I have no luck I might pop in to MLR as i'm in the area at least 2 days a week.

[DDdisco]

The way I could tell it was the fog lights is the tell-tale on the dash came on as well. It didn't matter what position the key was in.

[harlie]

DDdisco - whats the chance your horse float has a small battery onboard? (to operate breakaway brakes required for over 2000kg)

[DDdisco]

Yep, it does (quite a big battery actually). I thought that it may be a charge wire for that, but I've also got a built in charger that charges the battery when the float is plugged in to 240V to run the fridge, lights, etc. I also figured that the trailer plug wire was probably too small to be using as a charge wire for the battery anyway.

We always plug the float in at home before going anywhere to cool down the fridge, then plug it in again when we get there if camping. I also check the 12V internal lighting before going anywhere to make sure the battery has got enough charge for the breakaways.

Cheers

[harlie]

Yep, it does (quite a big battery actually). I thought that it may be a charge wire for that, but I've also got a built in charger that charges the battery when the float is plugged in to 240V to run the fridge, lights, etc. I also figured that the trailer plug wire was probably too small to be using as a charge wire for the battery anyway.

We always plug the float in at home before going anywhere to cool down the fridge, then plug it in again when we get there if camping. I also check the 12V internal lighting before going anywhere to make sure the battery has got enough charge for the breakaways.

Cheers
OK - usually if there is no other charging line (like a Andersen plug) the #2 pin is used as a trickle charger - the Aus standard for a 7 pin trailer plug is Aux or Reverse on pin #2. The Battery for the breakaway systems are normally very small (only9a/h) so the 7 core wiring isn't an issue, the point that some one added large batteries without changing this would be of some concern.

On the Float you have a charging wire on Pin#2 running straight to the battery (or maybe leaking through a fridge line ect)- when plugged in, it is powering the Rear Fog Lights which (same as my car) is on pin #2 on the car socket. I have cut and insulated that wire, about two inches from the Trailer Control Module, as no trailer that I have seen or heard of in Aus is fitted with rear Fog Lights.

I'm completely dumbfounded why the Land Rover dealers are delivering genuine fitted trailer wiring that doesn't conform to any trailers or standards in the country of sale - to the point where the owner is unable to legally tow larger trailers without modification - due to the tail lights on pin #5 issue as well as this one, there are ADRs that this is failing and we're not buying cheap Korean hatchbacks either are we...

[sniegy]

Harlie,
When the vehicle is not touched & no trailer brakes are fitted it is fine & conforms to Australian imports for a foreign vehicle.
As the wiring to the vehicle operates the things that are required.
R-turn 1
L-turn 4
Parkers 6
Earth 3
& Stop 7

The only 2 others that we use, as an "Auxilary" "If Required" are pin 2 (12v feed/rev/fog) & pin 5 (trailer brake feed/12v feed).

The dealers delivering these vehicles are NOT doing anything wrong.

If Mr Joe Bloggs purchased a vehicle to tow his trailer to the tip every weekend, he would not have a problem & NO modification would be required.
If you didnt fit trailer brakes again, you would not even know.:eek:

Cheers

[harlie]

If Mr Joe Bloggs purchased a vehicle to tow his trailer to the tip every weekend, he would not have a problem & NO modification would be required.
If you didnt fit trailer brakes again, you would not even know.

Cheers
Other than the continual message on the dash telling me my trailer tail lights need to be checked??? Because the car is wired with 2 tail light circuits to the trailer socket and no trailers in the country are setup like that.... I did only tow a box trailer to the tip at the start, and I did know something was wrong.

So what you are saying is that our Dealers advertise these vehicles as suitable to tow a box trailer to the tip and no more?

For a 100k+ vehicle that IS marketed as a series tow vehicle that's a bit poor. And as you know #5 IS required to tow anything over 750kg. My Vogue was wired for brakes by the Dealer with the instructions of 2000kg+ being required. When I took the car home I could not legally tow a heavy trailer with it due to this issue. We all know how much a RR Vogue costs + 1000 for the brake wiring and it still cannot legally tow a 2000kg+ trailer, which in today's standard is not that big!?!? It did at least fix the "Check Trailer Tail Lights" message....

Now I acknowledge that you are an invaluable member of this group and this is no way an attack on you, but do you really think that this equation is acceptable to the consumer? This is exactly why many people buy, and are even pushed (by van or marine industry) toward the Jap brands, and the LR dealer network, by treating consumers like I was stuffed around are even trying to push us enthusiasts away. As I said - why deliver a product, let alone an expensive product, that does not conform to any standard in the market of sale - just to p*ss people about? I've honestly got better things to do than try and work out what's wrong with my absurdly expensive towing wiring, because the dealer couldn't be bothered to do it properly. And this thread shows I'm not alone...

Note: Dealer in Q is not even in the same state as Sniegy

[sniegy]

Harlie,
I understand completey that this is NOT an attack on me.

I would say that frustration plays a big part in this & am sorry that you (&others) are not treated right & that the dealings are not what you anticipated.

I too would expect great things also when spending 100K+ or any money regardless for that matter on a vehicle.

If you need help, please feel free to ring me, am happy to help anyone when/where i can.

Cheers