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Discussion Starter · #1 ·
While out last night I turned the lights on and all was fine.
Then less than 3 seconds (literally) every went dead!!, light's, engine the lot!!.
It was if you'd turned the ignition off without removing the key.
It's fine when it's on the side light's but not "ordinary" light's, anyone know, I nearly hit a wall last night because of it.
 

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Could it be a bad earth back from one of the lights?

If the earth was bad it may be raising the voltage back on some of the other connected earth wires reducing the PD voltage seen by other components sucha as ecu's to below the running threshhold...

just a thought.

Andrew
 

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Sorry, PD = Potential Difference.

if the car battery is running a PD of 13.2v (standard). then that is the voltage all unregulated components see.

if you have a bad earth of a load consuming item, the voltage that component will 'see' will be lower as it attempts to earth backwards through several other earthed components. (you must have seen cars with bad earths on the rear ligts so that when the brake lights come on all tehe other lights come on dim etc).

If you have a light that has a bad earth and that earth point is shared by another component such as coil, ecu etc, you may find that the +ve side of that ignition critacal component is running +13.2v and the earth side may be running at +5v giving only 8.2v 'seen' by that component.

Andrew
 

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you could try pulling the 4 headlight fuses from under the bonnet and run the car, switch on the lights and see if it dies.

if it does then the problem is from the switch to the lighting fse box

if it does not, refit the fuses 1 by 1 until it does.

you will have then localised tha problem.

Andrew
 

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Discussion Starter · #10 ·
Thanks I'll try that with the fuses,


Zaphod.....I take it an auto spark would need a visit for that one!, or how do you check it yourself.


I dont get any battery lights or anything on before it happens, everything just simply goes out as if if you take the key out, very scary/weird.
 

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Not necessarily, David. If there has been a sudden brush failure or break then the charge light will not show at all. It may well be that there is just enough contact to allow a small drain as with sidelights, to find earth, but not a large.

Axl, The Black Box, Diode and Brush set have come as one unit for many years now, which you will be able to remove and inspect by the removal of securing screws (two from memory). Although the workshop manuals say you will have to remove gubbins to get to this and remove from the side of the alternator, it is possible to access by reaching from above and over the engine in about 10 minutes. I have even seen this done as a roadside repair.

This I stress may be the solution to your problem.

HTH
 

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Discussion Starter · #12 ·
I took the fuese out and the put the light's on and all was fine, put them back in and again all was fine.
What I should have said this problem doesn't everytime with the light's on, which makes it more of a PITA!!
 
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