Duetto 2004 Bathroom Light burnt out

jgd1584 wrote:Hello all...we were away in Yorkshire with our 2004 Mk6 Duetto. when all 12V lights failed & burnt smell from Bathroom! Have now removed light unit to see the pcb and feed wires totally frazzled and in a ball in the ceiling hole.
Also the 'Lights ' switch cannot be turned on .. just jumps back to off.. presumably a safety feature?

The AS wiring diagram I have only shows a single white wire running from the Lights switch to a box labelled LIGHTING, with no further lights wiring detail.
I'm guessing/hoping the feeds to the bathroom light run over the ceiling from the light at the rear of the aisle.. can anyone confirm this?
Also which fuse is on the (bathroom) lighting circuit so I can check it?
I have ordered a replacement light unit but need to figure out how best to access the wiring above ceiling with minimal cutting away to redo the wiring & connection...suggestions welcome!

Thanks very much  for any info....

Welcome to the forum - it's very likely that the switch that "jumps back to off" is the fuse. At that time, A/S were using a power control board (by MES, I think) that had combined switches and circuit breakers instead of separate switches and fuses. You can tell which switches are also circuit breakers by the red bar at the top, sometimes including the word "reset" in small letters. As far as I'm aware there are no other fuses in those circuits.

However, it sounds as though that particular circuit breaker may be defective, as they are supposed to be sized so that the wiring is not damaged in the case of a short-circuit! An alternative might be that someone has rewired at some stage and used wire that is too thin. That sounds unlikely, unless the wire that's in a ball is especially thin wire - which could have overheated partly because it was bundled up in a confined space?

Sadly it's also likely that you won't find anyone with a precise knowledge of the route that the wires take - each A/S conversion is hand-built and to a certain extent the installers make it up as they go along. When I had a similar problem, I could only infer the direction by pulling the wire tight in the hole and seeing which direction it went in. Don't pull too tight, as A/S typically used screw-down terminal blocks above the roof lining, and they aren't tooo robust... Sorry to be the bearer of bad news, but I ended up taking down the entire roof lining in my van!

[BTW - it's advisable to only use external text editors with care when composing messages here - your original message is full of [size=10] formatting instructions, which make it unreadable on my screen!! I edited all the [size10] instructions out of the quote of your text above to make it big enough to read.]

Thanks for info, albeit not much good news!  

I was thinking I may need to take down the Bathroom ceiling but hope to avoid by cutting a rectangular section out, leaving the fixing hole, and small enough to be hidden by the new fitment but large enough to get at the wiring...we shall see..

Are all the 12v light in parallel so some of the wires may be going off to say the spot next to the drop down flap?

Will have a close look at the switch but what you say certainly makes sense. 

Thanks again.. I will update in due course, using a simple text editor if not direct!

It's hard to know exactly how your van is wired. Mine had them all in parallel, but wired (IIRC from about 10 years ago) in a star out from a connector block above the ceiling panel. BUT it was not the same model (actually a Flair) and several years older, so they may have used different methods by the time yours was constructed.

One thing I would do though, if you haven't already, is to carefully pull the bundle of wire out of the ceiling hole and see if there is a join to thicker wire above the ceiling. If the bundled wiring was the weakness, it's very likely that the original loom will be unharmed - the wiring only has to be slightly thinner and it will be where the damage is concentrated.

OK .. looks like a few days project, minimum.. for me!
Thanks again

Glad to report that I today managed to pull the Ball of wires  down through the hole in the ceiling and what a mess, when I unravelled them ..see pic!

However the parallel feed wires wires easy to identify and after removal of old excess wires the new LED lamp wires were crimp connected ok and all pushed back up through the hole... but not in a ball!

I went for an identical fixing Labcraft  6w 24 led lamp, our first, and it is sparkly bright.. just right to see all the facial defects in the morning...

Still not sure what caused the short so I guess it must have been the jammed bathroom light switch which overheated even thought the light was not on and affected the PCB and wire ball immediately above. But I also now know the Lights switch has inbuilt protection... good. 

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Thanks for the update - looks like the factory-original loom survived well. As you say, it's really bad practice to bundle up lots of wire in such a small space.