Trailer reversing lights

**p38arover** · 25th December 2018, 09:36 AM

I just bought a secondhand trailer and replaced the crappy festoon bulb blinker/tail lights with LED units that have reversing lights as well. I also rewired the trailer to replace the crappy wiring. I know that's OK, I tested it all.

All works well except the reversing lights which don't work at all. Note my L322 has the factory fitted towbar and cabling, etc., not after market.

The owner's manual says nothing about the trailer module affecting the lights but the workshop manual says this:

The trailer module comprises a double transistor for reverse lamp and rear fog lamp operation and overload proof MOSFET circuit breakers for the following lamps:

l Left direction indicator
l Right direction indicator
l Brake lamps
l Left tail lamp
l Right tail lamp
l Permanent trailer battery supply circuits.

The above lamps are connected to the trailer module via direct connections to the applicable lamps. The rear fog lamps and reverse lamps are not directly connected to the lamps units because these lamps must be disabled when the trailer socket is connected.

I checked and the vehicle's rear fog and reverse lamps are not affected when the trailer is plugged in. Would someone who has a caravan with reversing lights (most trailers won't have them) be able to check theirs to see if their reverse lights on the van activate (and if the car's lights are extinguished), please? Ditto for rear fogs if fitted.

Oh, the electrical diagrams don't show the wiring to the trailer socket. They end at an internal plug.

**Roverlord off road spares** · 25th December 2018, 09:58 AM

maybe just tap into the wiring for the reverse light on the loom and connect that to your trailer wiring. I did this for my reverse camera.

**p38arover** · 25th December 2018, 10:03 AM

I could do that as I am already tapped in for my reverse camera but I'd like to leave the original trailer wiring untouched.

**Graeme** · 25th December 2018, 10:07 AM

Mine is MY12 which doesn't use a trailer light module so not a valid comparison with pre-MY10 vehicles but the reverse lights that I fitted to my van work. I can't recall if the car's reverse lights operate with the van attached. All the van lights are LED with load resistors fitted to the blinker circuits to stop the continual flashing implying that the RR knows that the van is attached.

**harlie** · 25th December 2018, 06:55 PM

2004 L322 doesn't have reverse lights in the trailer harness - you need to tap into the main tail light harness.

Newer cars have reversing light in the white socket.

**p38arover** · 25th December 2018, 08:54 PM

Thanks Harlie.

Then the 2001 workshop manual lies!

Reverse Lamp
The reverse lamp function of the trailer ECU is controlled via a bi-directional data line
between the LCM (C2040) and the trailer ECU (C0380) on a UNY wire. When the trailer ECU
receives a reverse lamp signal, it provides a feed to the trailer socket (C0499) on a YU wire.

Trailer Socket Wiring.jpg

I'll have to delve into the wiring.

I can't find a diagram for connector P124

**BigJon** · 25th December 2018, 10:09 PM

As Harlie said, on my 07 I pulled reverse light power from the white socket. I use it for my camper trailer reverse lights and for an extra LED reverse light mounted under the rear bumper. Using the original wiring would trigger a bulb warning.

**p38arover** · 26th December 2018, 07:54 AM

The '04 only has the black 12N socket. I'll open up the socket and look inside.

**harlie** · 27th December 2018, 08:14 PM

It's not in the black socket... In standard form it has:
2 indicators + 2 tail lights + 1 brake light + 1 fog light + 1 earth.

Mine now has the standard 5 + trailer brakes + reverse (which we would call the standard 7?). Harness is changed about 50mm from the trailer ECU.

Early L322s sold in Aus don't have the white socket (they did in the UK) - so the diagram in RAVE is not completely wrong - we are just missing the white socket.

Easiest place to pick it up is in the loom that comes from the LCM, runs past the trailer ECU towards the underfloor (spare tyre) space. you will also need the reverse light wire to trigger the relay that will power the reversing camera

. Due to the bulb check, you can't power a camera directly from the reverse light wire - same applies for LED reversing light.

**p38arover** · 28th December 2018, 12:46 PM

I didn't look to see if the trailer reversing lights came on when the rear fogs were switched on. It appears the UK uses pin 2 for fogs and Oz uses pin 2 for reversing lights. I might reconfigure the wiring in the wheel well. I already have a tap on the reverse wiring for a rear camera relay that switches the TV module to the AV input which has the camera output.

EDIT: Yes, the trailer reversing lights come on with the rear foglights.

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