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Joined: Dec 29 2016
Posts: 357

Evening all,

I’m about to use my P38 for towing a caravan and am considering changing the towing electrics.

My P38 currently has the black 7N towing socket on the back bumper. It’s a genuine LR socket on it, from reading online it’s likely connected behind the tail light cluster on the OS of the car.

I’m thinking of adding the white 7S socket so I can run all of the caravan electrics properly. From reading on the net, I gather there’s a socket for that to connect to behind the tail light cluster on the NS of the car. There appears to be 2 part numbers when looking online...

AMR3007 - Towing Harness
PRC9233 - 12S Towing Socket

From what I can gather, AMR3007 plugs into the plug behind the light cluster and PRC9233 connects to this to give you the additional socket. I’ve read there’s also an additional relay that you need to add to stop it flattening the car battery.

I’m thinking of combining both the 12N and 12S sockets into a 13pin electrical socket on the back of the car as well.

Does anyone have any experience of the 12S socket on the P38?

Thanks,

David.

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Joined: Dec 30 2015
Posts: 4704

The extra socket on the NS has permanent power, ignition switched power, reversing light power and ground in it. I've used it to pick up a feed for a reversing camera and for a pair of additional power sockets in the boot. I've still got the original 7 pin trailer socket though.

Member
Joined: Jan 16 2016
Posts: 375

It is so long ago since I did mine. I have owned the car for 18 years now and I bought it with a towing bracket and just a black 12N plug.
I put a 12S socket on later along with a removeable towing bracket.
I remember buying an aftermarket control box for the 12S socket but it didn't work. I don't remember fitting a relay to the car. The caravan has a habitation relay which cuts the caravan battery when it detects the car engine running. You may be confusing it with that. Not all caravans have them.
The 12S socket has a permanent 12v on one of the pins and I remember running a separate heavy duty fused supply straight from the battery. I made up a plug and I charge the car through the 12s socket now. Sorry it is not more help. Must have been 15 years ago.

Member
Joined: Feb 11 2018
Posts: 357

Mine has an aftermarket charging system with genuine lr voltage sensitive split charge relay near the battery.

https://www.google.com/search?q=voltage+sensitive+relay&oq=voltage+se&aqs=chrome.1.69i57j0l3.3670j0j7&client=ms-android-samsung&sourceid=chrome-mobile&ie=UTF-8

A bit odd but works.

Member
Joined: Feb 25 2020
Posts: 155

Mine did not had the tow bar or electrics, I bought a Witter flange type and a second hand AMR3007 with a round 7-pin connector. Installation was super-easy and needed no additional efforts.
I did not go for a 13-pin simply because I could not find one ...

Look online for instructions or information on STC8875AB "Split Charge Unit", this is (was) the official towing kit which included this relay you are talking about. If you can't find it, I can send it to you (actually I could load it up in the library if I knew how ...)

Member
Joined: Dec 29 2016
Posts: 357

I've managed to track down the last genuine STC8875AB from Land Rover at a cost of £148 + VAT. With a bit of luck I'll be able to source a relay and make another kit for the other P38.

David.

Member
Joined: Dec 29 2016
Posts: 357

I called a friendly Land Rover dealer the other day when I was looking for a split charge kit. They advised me that the kit for the P38 is obsolete and has been for a number of years. However, they did say that they had 1 kit left at the factory. I managed to get my hands on it and it was delivered this morning.

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I wanted 2 of them, one for each of our Vogue SE’s but it obviously wasn’t meant to be. It’s not a particularly difficult loom though so I’m going to buy a couple of the relays and will make another loom.

David.

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Joined: Dec 30 2015
Posts: 4704

Have you seen the price of that voltage sensing relay????? https://www.brit-car.co.uk/product.php/89705/4590/voltage_sensitive_switch____defender___discovery___range_rover_classic

I'd go for one of these instead https://www.autoelectricsupplies.co.uk/product/925/category/149, may be overkill at 140A but will do the same job (unless you can find a lower current version at sensible money).

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Joined: Dec 29 2016
Posts: 357

It’s horrendously expensive, isn’t it!