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Discussion Starter #1
Could somebody please help me find a wiring diagram for the courtesy lighting, it's a T5.1.

I'm fitting 6 spot lights in the back and I've been requested to have only 2 of them illuminate when opening a door.
 

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Discussion Starter #2 (Edited)
OK, I shall amuse myself and hopefully help someone in the future.
After a bit of a play with my multimeter and after a search on here I was able to work out what's going on.

To each of the rear courtesy lights (and probably the front one) there are 3 wires.....

Red/black: Live (12v) and is switched on by the Body Control Module (BCM) when the vehicle is unlocked or a door opened, this is for approx 20 mins. Is also live when ignition is on.
Brown/red: Earth,and is switched on by BCM when vehicle is unlocked or a door opened, but switches off (ie no longer to earth) with ignition on.
Brown wire: Earth permanently .

I had hooked up a new side step light to the red/black wire and brown wire initially and thought this was working correctly until my partner drove to work the next day and it stayed on for the whole journey.
After testing further I worked out the arrangement as above, and swapped from the brown to the brown/red wire and now it works perfectly.

I then had to sort out a way to illuminate 2 of the LED lights she had bought by opening the doors, she then changed her mind and said just one near the barn doors at the back would be good.
It turns out the BCM doesn't like LEDs, I also managed to pop a fuse which took out the rear sidelights, F17, it's a 7.5Amp.
So I installed a relay, it's switched by the BCM and this turns on one of the LEDs powered by the leisure battery. I also installed a diode before the LED on each circuit to prevent feedback and illuminating the other LEDs.

The other 5 LEDs plus this one all illuminate via a separate switch and are powered by the leisure battery.
 

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Hi Maro

Cheers for posting the follow up - it's almost exactly what I want to do! I'm planning to install 6 downlighters, with the ones nearest the barn doors and sliding door working as courtesy lights.

I'm not too knowledgable about this subject though so I've got some questions if you can spare a bit of advice? 😇

What are the specs for the the relays and diodes you used?
Do the courtesy lights have two live feeds - one from the BCM and one from the leisure battery?
Do the courtesy lights earth via the BCM and the rest of the downlighters earth elsewhere (body/leisure battery)?

Thanks loads!
 

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Discussion Starter #4
All the downlighters (6 in my case) earth to body.

The single downlighter that illuminates from BCM has 2 live feeds, both from the leisure battery, one is via a switch that operates them all, and the other feed is switched by the relay. The relay is switched by the BCM, both the live and the switched earth.

I have removed the courtesy lights in the rear, and used the wires for one of them to control a new side step light.

Diode

This type of relay

Terminals 85 & 86 are for the BCM,
Terminal 30 is live feed.
Terminal 87 goes to the light.

Hope this helps.
 

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Hi Maro,

Thanks for your post.

You've pointed me in the right direction to wire in my side step lights today and they work a treat. The BCM didn't seem to mind my LED step lights and they have a nice gentle on with a dimming off which is a real bonus. Hopefully they'll stay like this and a relay won't be required at a later date.

Thanks again!

Phil.
 
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