On a cherokee sport diesel what colour wire do i connect the white earth return to at the taillight, 2006 model this is from the trailer connection socket

Trailer lighting is notoriously unreliable, especially on commercially manufactured and wired trailers where the manufacturer tries to save money by using a chassis or body earth return instead of a fully wired system and the better quality lamps such a system would require.

In my experience eight out of ten trailer lighting problems are related to a ground or earthing fault or poor quality wire and poor quality terminals being used.
The other two out of ten related to problems with the plug and socket connection (car to trailer).

This is assuming the towing vehicle had the tow socket wired to a high standard in the first place and didn't use the notorious Scotchloc.
The Scotchloc device was adequate for some of the wiring to older vehicles that used thickly insulated thick wiring but they are totally unsuitable for wiring connections that are exposed to movement, dirt and moisture and the thin wiring of the modern vehicle. There are in addition to the blue coloured ones, also red and white more suited to thinner wiring and also a brown one for larger cables but blue seems to be the ones supplied most often and so these are the ones used most often and consequently are responsible for quite a lot of faults where a supply doesn't even reach the tow socket.

When searching for a fault it is best to check the towing vehicle electrics and the trailer separately. Plugging in a known good trailer or lighting board is the best way to check the car socket. I have made a box of tricks for checking both the car and trailer separately, including the grounds and supplies for fridge, battery charging, etc. It will also, with the aid of a lighting board, provide lighting to a towed vehicle that would otherwise have to be trailered.

Get the wiring standard for trailer socket on car / caravan .
Something like this
http://www.caravantalk.co.uk/caravan-advice/new-to-caravanning/electrics-guide/12-volt-systems
Then get a 12v probe and test the voltage is coming out the correct pins on the car when the tail lights are turned on.
http://www.amazon.com/6-36V-Circuit-Test-Probe-Indicator/dp/B0065R1CK4
Check the Earth Connections on the caravans tail lights.
Check the Caravan has an earth connection to the car body.
https://caravanchronicles.files.wordpress.com/2012/01/caravanchronicles-wiring1.jpg
see how pin 3 shows an earth wire it would have a wire on car socket pin 3 going to the car body. If the earth wire is corroded or broken I think the tail lights on the caravan would not work. It may be a different pin on your setup .

The 4-wire flat plugs usually have a white (ground), green (right brake/turn) yellow (left brake/turn) and brown (taillights - left and right). If your brake and turn lights work but the taillights don't, check the plugs (trailer and truck sides) for corrosion, and chek both the trailer and truck wiring harnesses for chafed insulation and bare conductors on the brown wires. Likewiae if the taillights work and the brake/turn lights don't, perform the same checks on those wires. And last but not least, be sure that the white wires (truck and trailer) are grounded well to the truck body and trailer frame.

Forget the fuses to begin with - you need to check each wire with a multimeter with the lights and ignition turned on to see whats happening at the plug end.

No multimeter? then get a 12v test lamp - (check first its working when connected to the battery it works). Now start with say the Tail lights on - connect the single wire from the test lamp to earth (a clean solid metal connection - like towbar) and then press the probe end against each wire in turn until you find the probe light turns or not. If it turns on then mark that wire as Tail - now do the same with the Stop light, then each Right/Left Indicator and then with the Brake light - either have someone press on the foot brake or else jam a suitable sized length of wood between the bottom of the steering wheel and the footbrake to hold it right down. You may also have a Reverse light as well.

You must have ignition ON to check, Stop, Reverse and Turn Indicator lights.
Hopefully this will locate each 'working' wire for you. Then you have to connect these to your trailer plug in the correct position - Google on your area if need be to see what pins are connected to what wires else when you plug the trailer in to the plug it still won't work.
Check out this website for pins and colours - make sure its applicable to your country - http://www.etrailer.com/faq-wiring.aspx as it may differ from country and vehicle..

If you find any wire that does not light up when probed - then check the fuse for that wire's use - ie. Tail etc. If that fuse is ok then check back from the plug to the fuse box as you may have a broken wire or disconnected plug. You will always have an Earth wire - this will not light up when probed - its colour is normally white.

Your best bet is to go to an auto parts store or dealer and see if they have an adapter for trailer lights. Most of the newer vehicles have adapters the just plug into the existing wiring harness and you don't need to worry about splicing things. Also on some vehicles hooking up directly to the wiring harness doesn't work too well because of the circuit not being able to support the extra voltage drop. The adapter usually have that taken care of.

If the other lights work on the trailer, it won;t be the earth return. Probably you have not wired the car connection to the same key as the trailer and your running lights are connected to pin 5 or the aux pin.

Hi there,

Here is a cheat sheet I compiled that you will find very helpful:


Plug Types/Application
7 Way - RV Trailers, Horse and Utility Trailers
6 Way - Horse, Stock and Utility
4 Way - Utility Trailers

Columns are Color, Function, Mark on the plug.

Seven wire Trailer plugs:

Horse, stock or utility trailers:
White = Ground - 1
Blue = Electric Brakes - 2
Brown = Tail and clearance lights - 3
Black = Battery, aux power - 4
Yellow = Left turn/Brake - 5
Green = Right turn Brake - 6
Orange or Purple (not both) = Auxilliary or Reverse - 7

Recreational Vehicle:
White = Ground - 1
Blue = Electric Brakes - 2
Green = Tail and clearance lights - 3
Black = Battery, aux power - 4
Red = Left turn/Brake - 5
Brown = Right turn Brake - 6
Yellow = Auxilliary or Reverse - 7


Six wire trailer plugs:

Horse, stock or utility trailers:
White = Ground - GD
Yellow = Left turn/Brake -LT
Green = Right turn Brake -RT
Brown = Tail and clearance lights - TM
Red or Black (not both) = Battery, aux power - A
Blue = Electric Brakes - S

Recreational Vehicle: (color, use, plug mark)
White = Ground - GD
Yellow = Not used -
Brown = Right turn Brake - RT
Green = Tail and clearance lights -TM
Black = Battery, aux power - A
Red = Left turn/Brake - LT
Blue = Electric Brakes - S


Four wire plugs:
White = Ground
Yellow = Left turn/Brake
Green = Right turn Brake
Brown = Tail and clearance lights


Ground should be 10ga.
Others 14 ga

Best regards
Mike

Hi ebrown80
You can splice into each wire in turn at the back of the lamps.No need to cut right through the origional loom completly. For a really good joint you should spot solder each connection and insulate all joints well. Tow bar sockets operate on a common earth, so no need to loop each one.
Check back of socket and you will find each pin has a number. 1---7
The wiring colours from the socket back to the loom are as follows
No 1 Pin--- Yellow Wire---Left Side Flasher
No 2 Pin--- Blue Wire------Fog Lamp.
No 3 Pin--- White Wire--- Earth. Must have good contact or nothing else will operate.
No 4 Pin----Green Wire--- Right Side Flasher.
No 5 Pin----Brown Wire---- Left Side Park Light
No 6 Pin----Red Wire-------Brake Lights
No 7 Pin----Black Wire----Right Side Park Light. Centre Pin.
I hope this helps you out
Best of Luck with it
John

If you have access to a digital multimeter or test light, check if there is power going to the plug, if there is then maybe the trailer plug and the truck plug dont match up

The connectors for towing wire harnesses on foresters are generally on the passenger side, below the rear taillight inside the cargo space. some require pulling up the foam block that is between the spare tire compartment and the taillight. Check where you replace the tailights from inside the car, if there isn't a matching connector hanging out there, check around the spare tire compartment, see if you can remove the carpeted foam block next to the compartment and find the plug under there.