Citroen xsara 2002.
Hi anyone know why my rear wiper starts when I brake, And the top light gets dimmer every time the blade moves eventhough its not turned on? I have cleaned all rear lights and it made no diffence. Also if i turn on the wiper on and then brake the top boot light does not work straigt away.Or when the headlights are on the wiper struggles to work???

kevin, March 2013

I think if you check below that it's Kevin who brings up the subject of a Green & Yellow wire. It suggests to me that somebody has been doing a bit of re-wiring with some household wire - and things might have gone wrong.

I accept that French cars might have some quality issues - I know a senior Quality Specialist in the auto industry - it's usually down to cost reduction - last time we met I heard about (would you believe it) Poor Earth Bolt fittings at JLR !

I can understand water ingress causing bizarre faults with vehicle electrics - where I have difficulty is accepting that a "bad earth" on circuit A can cause circuit B to misbehave. I have seen it advocated several times on here and have asked for an explanation (to gain knowledge) but no explanation has been offered - it's not a case of not believing - just not understanding.

I know a bit about Concord wiring but not much at all about French cars...

Peccavi, March 2013

maybe on your vehicle the earth path is through tailgate hinges? if so i would run a new wire from tailgate to body earth to by-pass hinge [which could be your fault]

k, March 2013

peccavi green and yellow wire is only used in 240 volts mains wiring,not in car earth (have you been drin king your barley wine ??)ford use brown wire for earth wire,dont know what te french use for their trash cars,but they do not have sa good rep for their electrics in cars i have repaired lots of french heaps for the eletrics and its mostly water penetration that causes shorts circuits in the lighting clusters renult for instant have a know fault that causes the electric window motor to s/c at a cost of £139 to replace,water gets into the motor thy know about this faukt still they do nothing to hlp

mm, March 2013

There is a green yellow wire (I pressume Earth) coming fromthe lid brake light to the wiper motor, and two other purpel wires that come from the front of the car. I tested the wires and there is a current traveling the thinner of the purple wires when i press the brake. ( if I unplug the wiper the lid light does not work)

kevin, March 2013

The French built Concord - they got that mostly right...

Now I challenge this "Earth Fault" theory... On a car earth is just the return path to complete the circuit back to battery negative - it saves weight and the cost of wire. If the earth is good then the circuit works and if the earth is bad then it's like an open switch - the circuit does not work.

An open switch (bad earth) can't make a different circuit suddenly start working - not when I learnt about electricity.

No this fault smacks of crossed connections or even a short between one circuit and another and dimming lights suggests things wired up in series.

I suspect that the work experience person has been fiddling around with the electrical connections.

And it would be neat to know just how a bad earth can make something operate that shouldn't be operating.

But of course - I could be wrong - and often am.

Peccavi, March 2013

you posted twice i see,i told you it was french rubbish

mm, March 2013