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Parts Needed to Install a 7-Way Trailer Connector to a 2003 Land Rover Discovery II


My LandRover has factory installed trailer connection plug in the right rear tail light. I purchased the harness. All plugs fit and matchup. However, there are 3 wires sticking out of the harness attached to nothing which end behind the tail light lensewhere the connetion is Where do I connect the 3 wires that are coming out the side of the harness?The harness kit from Dealer has an adaptor included to convert from the factory 7 round to a 4 flat to a 7 flat which matches the trailer male plug. I dont think all pins are matching each other wire purpose with the correct wire. In turn, I needed an adaptor from Pollak # 12-723EV to connect this and also to connect to the trailers 7 blade, plug. The adaptor from Pollak also has 3 wires 4counting the white ground wire the 3 wires are purple, blue and black.I have no trailer lights at all when plugged in. My question: Where do the 3 wires sticking out of harness on vehicle side and the 3 wires on the Pollak adaptor go? Do I connect them together ? Both 4 flat connections vehicleandtrailer adaptors wires match color to color brown,white,greenandyellow Also, is it okay to change the trailers wire,pin location to match the adaptor #12-723EV ? Since the two 4 Flat connections seem to match, I dont want to cut, splice and possibly alter the vehicle sidewiring,harness ect.. Thank you for your help!!


Expert Reply:

You can determine the wire functions on the vehicle by testing them with a circuit tester like # 40376. The wire that shows 12 volt power all the time is the hot lead, the wire that only comes on with the reverse lights is the reverse light circuit, the last wire will be for brake controller out put.

The wiring harness I show for a 2003 Land Rover Discovery II is # 119178KIT which would require splicing into the vehicle wiring behind the tail lights. It sounds like you are using a different harness. When adding a 7-Way to this vehicle, we recommend the above wiring harness and a 7-Way trailer connector using # ETBC7.

With the ETBC7, you will plug in the 4-Way to the back of the unit. The white wire will need to ground to the vehicle frame, the purple wire connects to the reverse light circuit, the blue wire is output from a brake controller, and the black wire connects to the vehicle battery via a 40 amp circuit breaker. I have included some links that will help explain an ETBC7 installation.

It sounds like the harness you have has wires for 12 volt power, brake output, and reverse lights. On a 7-Way, they will connect to the back of the plug as follows:

12 volt = pin in 11 oclock position
brake = pin in 7 oclock position
reverse lights = center pin

I have included a link to a wiring FAQ that should help. You will need a circuit tester like # 3808, to test vehicle side wires for function. It is fine to change the pin out on the trailer side connector to match the adapter.

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