Short circuit - making me short circuit!

[Alan Stirrup]

Hi all,


I do hope you can help me with my 2014 Fiat Fiorino.


I have a short circuit which has stopped the rear tail light and front side light from working. when the lights are on, ignition is on but the engine isn't running the lights work, the lights work whilst the heater plug light is switched on but as soon as the heater plug light goes off and the engine starts the lights go off. If I turn on the lights whilst the engine is running the come on for a split second and the go off.


I can't get an auto electrician to look at it until later this week and I've already been pulled by the boys in blue because of it so I can't chance driving it until it's fixed and I need it for work.


I've attached a pic of a diagnostic that my pal did with the error codes that are flagging up. Any help would be greatly appreciated and save me from short circuiting!


Cheers
Alan.
Attached Thumbnails

 

[shaun1]

Sorry, i don't know the vehicle, but looking at those codes it looks like the problem is in the rear left light cluster or cabling to/from it. I would take the light clusters off on both sides (as the loom normally runs from one side to the other) and check for any damage to the loom or water in the connectors etc. Make sure everything is seated properly and clean and dry.

I would then check the earthing point(s) (a common cause of lighting issues). This could be pulling things up and down depending on what lights are on and throwing all sorts of errors.

If that doesn't come up with anything, try amd trace the looms back as far as possible, again checking for connections and damage to the looms.

If you have a multimeter, you could have a go at measuring voltages between each +12v and ground with the lights on to see whats coming through.

 

[PEG]

Hi,if the lights function OK,before starting,it rules out the units,lamps,and SOME,of the wiring.

It sounds like an electronic mishap,CanBus issue,or similar.

Any common faults on the model specific forum?

 

[shaun1]

Hi,if the lights function OK,before starting,it rules out the units,lamps,and SOME,of the wiring.

It sounds like an electronic mishap,CanBus issue,or similar.

Any common faults on the model specific forum?

Sorry I forgot about that bit. Would expect to see error codes like failure to communicate with modules etc, if there was a fault on the can bus. Some cars run sidelights at a lower voltage when the ignition is off, so that could be why they fail at that point.

 

[Alan Stirrup]

Thanks Guys,
I do appreciate your help. Something I noticed when I took off the rear light cluster to check the bulb, the reversing light section was cracked and had filled with water. When I took the back bulb holder off there was quite a bit of corrosion around the bulb terminal, could this contribute to the problem?

 

[Alan Stirrup]

I have access to a multi meter but have never used one, what settings should I put it on please?

 

[shaun1]

Yes that could well be an issue. Is there corrosion/moisture on the connector from the loom?

The fault may appear with the engine running because of the extra few volts from the alternator. Do you have a multimeter?

 

[PEG]

If there is water in there,it can play havoc,with the various systems,designed to sense faults,and it also can migrate down multi-strand cables,all the way to connectors and other ECU components.

Be careful sticking test probes in,as not only can the readings be meaningless,there is also the chance of damaging some components.

 

[Alan Stirrup]

Thanks Peg I'll steer clear of random stabbing. Shaun, yes I have access to a multi meter but don'y know what setting to use it on? Thanks for your help so far guys - much appreciated.

 

[gnuuser]

corrosion of connectors are also a common cause of vehicle electrical fires.
if its just a patina you can easily clean it up with a good quality contact cleaner
but if the corrosion is significant enough that you need to scrape it off then there's a good chance they are too weak for proper connection and should be replaced as soon as possible.