Technical Rear fog light /reversing light problem

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Technical Rear fog light /reversing light problem

seemore

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Hi all
can anyone help me please.
I have a 2007 fiat ducato 130 multijet based motorhome.
The problem I have is that when I switch the rear foglight on the indicator on the instrument panel says that it is on but it is not.:mad:
I made sure that I have the headlights on but no joy.

If I put the vehicle in reverse the fog light comes on as well as the reversing light so it is not a faulty lamp.
Any help will be appreciated


Seemore(y)
 
Last edited:
Vans made by a Continental MH manufacturer have the rear light cluster and the associated bulbs within the lens unit round one way, and UK MH manufacturers the light cluster arrangement is the opposite. To resolve the situation the offside cluster should be moved to the nearside, and nearside to the offside, the backlights, brake lights and indicators will remain the same, and the power supply to the fog light, and the power to the reverse light will be on the correct side and will then work as they should.
 
I should add that I'm assuming that the fog lamp bulb is in one rear light cluster, and the reverse light bulb is in the other. Hope all this makes sense !!
 
Sorry guys but I forgot to mention that when I put it in reverse both the reversing light and the fog light are on.
This problem has only occurred recently and I have not done any alterations to any of the lights etc.

Seemore
 
Gareth : You are correct, I just assumed maybe that it was an EU made vehicle in which case it would have been around the other way.....I was wrong !

Seemore : I think then that you've probably simply got a short somewhere.
 
Sorry guys but I forgot to mention that when I put it in reverse both the reversing light and the fog light are on.
This problem has only occurred recently and I have not done any alterations to any of the lights etc.

Seemore

What model is it?
 
The usual cause of spurious problems in the rear light clusters is faulty earths, both individual bulbs to holder as well as holder to chassis; it is well worth checking these before looking for more complicated solutions.
 
Check all bulb holders & connections in light clusters.
Is it wired for a tow bar???
Check the plug for corrosion & where ever the towbar wiring was attached.
 
Gareth:
I checked all the holders and made sure that they are all earthing ok.
There is no tow bar fitted.

Crossingkeeper:
I checked for bad earths but all lamps light up ok.
The rear cluster is Hella Caraluna MK2 They have horrible plastic lampholders that clip in to the backplate which is also where they are all earthed. I have pinched a piece of plastic behind each lug so that they cannot pop out with vibration etc to make sure they get a good earth.:bang:
Shingy:
Could be a short somewhere but I am having trouble tracking the wiring loom. Any ideas?
 
I'd trace the wire back from the lamp to where the body builders wiring joins the original chassis wires, I know Fiat have been building special motorhome chassis for some time so its possible that they supplied them with long cables to avoid such a join though :\
 
Gareth
I will try taking the reversing lamp out and let you know.
If I can get underneath tomorrow I will try to find the joint to check it out.

I appreciate your help(y)

Cheers
Seemore
 
No worries, I used to work on buses a lot, always getting earth faults on tail lamp units,
Also, if there are any sharp metal bits inside the lamp units make sure no wires have rubbed through against them ;)
 
One final point before bed DO NOT use a volt meter if testing circuits! Use a test lamp pref with a 21w bulb in!
Meters test for voltage, I've seen a circuit check out with a meter but instantly fail to pass current once loaded with a bulb ;)
 
Gareth
Latest update: I took the reversing light lamp out and the fog light still came on!:bang:.
Not one to be beaten easily I then inspected the wiring and found that the wire that connects to the reversing lamp holder is then looped across to the other rear cluster to the fog lamp holder. sounds stupid! this is the original wiring.
No wonder that they are coming on together!

The bit I don't understand is that this obviously has always been wired like this yet I am sure this fault was not there 2 years ago when I bought the vehicle as I did a pre MOT check and I would have noticed it.

I thought that maybe there was a relay switching between the 2 but it seems impossible if they are connected with the same wire. Doesn't it?:mad:

On the other point: I checked the wiring loom and found out the route that it takes and there is only one joint which looks ok.

Number plate lights not working:
I tested every fuse in the box concealed blow the steering wheel and they are all ok yet there is no power to the rear number plate lights.

I cannot find any other fuse box apart from the main one under the bonnet, I have a very basic schematic wiring diagram which shows something called a "Short circuit coupling" but it does not say where it is. Have you ever heard of this?
Sorry to have rambled on.

Seemore
 
"Light bulb"!! Are the fog & reverse lamps separate units? Not built into the cluster? If so are the lenses interchangeable???
Is it just that someone has swapped the lenses over??
Number plate lamps will pick up of one or both tail lamps, I've never found a vehicle with a separate circuit! Dollars to doughnuts you have a broken wire back there.
Never heard of a short circuit coupling!! Try running it through Google translate into Italian & back to English!!
 
I think you should take this whole issue back to basics. I would remove the light cluster on each side. Make a sketch of the wire colours to each bulb holder, then remove all the individual wires. Check each wire in turn with a 12v bulb to ascertain what's live and what's not under each "switched on" condition. You will then know what wire is live and which bulb it should be illuminating at any given time. Go for it !
 
Shingy
I have already taken it back to basics as you say and checked them all individually.
To clear things up : on the nearside cluster I have . Stop/tail light then the standard reflector followed by the indicator then finally the reversing lamp.
There are 2 wires into Stop/tail light. 1 into the indicator then 1 into the reversing lamp which then passes across to the fog light in the offside cluster. Offside cluster also has 1 wire into the indicator and 2 into the stop/tail light.
All the lights are working perfectly except for the fact that the fog light lights up when reverse gear is engaged along with the reversing lamp. They are wired to each other! a purple wire goes to the reverse lamp holder and another purple wire is crimped with this on the standard lunar lug and then crosses over the opposite cluster to the fog light.:bang:

Seemore
 
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