number plate lighting

[phirouyer]

I noticed some time ago that the number plate light on the right handside was off. I checked the bulb : it was ok. Since this is not a reason for MOT failure (at least in France, as long as the left light is OK) I left it for a while. Then, I had a closer look, undoing the trim of the boot lid. The connections were ok, but there was no current on the wire. I could see that the right light is independant from the left one. The wires are in good order and rejoin a harness which goes ... well, somewhere. As I said, this is not a big issue and I can live with it. But I am curious to know what could be the reason. There was no point in checking the fuses : both lights share the same fuse. Could it be that the lights may be connected to some faulty electronic board ?
Philippe Rouyer, X308

[BrianG]

The favourite place for any electrical faults on the X308 boot lid area is the main wiring loom where it loops around the right hand hinge. The most common fault is with the boot release button circuit, but any of the wires in that loom are potentially liable to fail with time. Although the loom is clipped to a shaped plastic piece around the hinge this is not a good design for strain relief. The wires sometimes are obviously broken where the loom leaves the plastic clip and goes into the car body: these can then be identified and repaired, however more difficult to find are those that have broken inside the insulation without breaking the plastic outer covering. I have found the only way to locate such a break is to probe down the length of the suspect wire with a multimeter and a sharp pin. Turn the side lights on and connect the negative test lead to ground; using a pin connected to the positive test lead carefully push the pin through the insulation at points along the wire until you find the place where the 12V disappears at the break.
I personally favour unclipping the wire loop around the hinge and let it find its own path into the car body as this seems to minimise repeat wire breakages after repair.

[phirouyer]

Thank you Brian, this is exactly what I feared. The broken section must be under the covering of the loom. I think I will leave it as it is, since I have still one good light and this is not a cause for MOT failure. - This kind of problem was easier to locate on the XJ40. In some respect, I miss my old 40 !

[ptjs1]

Philippe,

Why not just wire to the broken light from the working light and not worry about the original break?

Paul

[Brakebuster]

Philippe,

Why not just wire to the broken light from the working light and not worry about the original break?

Paul

from memory , the lamps have a permanent live wire going to them , and operate by way of the boot light switch making the circuit to ground ,

this may ( or maynot ) help ,

the loom problem point is well worth investigating, because , if one wire is giving issues, a few others may not be far behind, this can manifest its self in a locked boot , or a short in the wiring causing other issues , I had to do the repair on my own X308 many years ago ( 9 ? ) , and there is a post on it here on the site

BB

[phirouyer]

I have thought of wiring to the working light. I would have done it if it had been a reason for MOT failure, but honestly I don't really care if one of the lights is off.
Now I agree that other wires in the loom may fail in the future and it might be worth investigating the loom. But I can see the leaves falling. Winter is coming and this is a Spring job ! A job you do on your drive on the sunny day...