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D3 - Lights Headlights, xenons, foglights. Everything outside the car that glows

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Old 26th April 2017, 06:20 PM
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Default Failed supply to LH Reverse light

My left reverse light has stopped working, right is OK.
No voltage to LH reverse bulb.
Are they fused seperately?
Any ideas please.
I have had a look at the current flow diagrams and I get lost when back at the control unit.
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Old 27th April 2017, 04:50 PM
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I think this is component protection Ray. The thing knows it's been fitted with a non OEM screw.
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Old 27th April 2017, 05:36 PM
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Do you think the LED bulbs may have caused the ECU to cut power to the bulb? I think it does the same for the number plate lights when certain LEDs are fitted.

Did you fit the resistors?
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Old 27th April 2017, 06:09 PM
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John, Tony,
You do not realise how close you are to the possible problem.
Earlier today whilst battling the bus full of school kids through traffic my mind started pondering and came up with the idea that maybe the non-OEM led had broken and shorting the supply to earth. The ECU theoretically should limit the current flow through it's short circuit protection system by dropping the supply voltage to the faulty bulb to virtually zero volts. This would match my symptoms so Sturday's first plan is to strip the inner left light unit and check the LED bulb. If it has gone short circuit then I guess the OEM filament bulbs are gonna have to be refitted.
Shame really 'cos the light output of the LEDs is much better than the OEMs.
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Old 27th April 2017, 08:54 PM
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It's a real shame if it does end up being the LEDs, Ray.

If you haven't already, would you consider fitting the resistor, or even a bulb in series?
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Old 28th April 2017, 07:19 PM
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Not that easy unfortunately.
A resistor in series would prevent the short circuit LED affecting the rest of the circuit (I have taken a link from the LH reverse light feed to operate my non-OEM camera) but would decrease the voltage available for the LED when working correctly.
The extra resistor/bulb idea is to wire in parallel with the LED to fool the ECU into thinking that it is a normal bulb. The ECU thinks the lamp is open circuit because the LED draws much less current than the correct filament bulb.
I use a parallel bulb in my sidelights for this and hide the extra bulb behind the headlight reflector. This has a problem if the LED fails open circuit you do not know without checking the lights the old fashioned way (walking round the car). If the LED dies short circuit then you have the type of problem I have now. The reverse light is a more major job 'cos you have to drop the boot lid lining etc. to get at it.
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Old 29th April 2017, 06:10 PM
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Had an 05:00 to Morecambe then an 09:30 to Liverpool wait and return.
Between them I had one hour thirty minutes which gave me enough time to look at the problem. Resolved to a short circuit LED on the nearside. As soon as I disconnected the bulb the supply voltage lifted to the nominal 12 volt and the camera started working.
So while the boot lining was off I refitted the original filament reversing light bulbs.
Shame 'cos the LEDs were really good lightwise but obviously no good on reliability.
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Old 29th April 2017, 07:38 PM
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Sorry to hear that Ray, I had high hopes for those bulbs.

Sorry also for my brain-fart, I meant in parallel, of course.

I wonder if wiring in the resistor would help with the reliability by smoothing out the current going to the bulb?
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Old 29th April 2017, 09:08 PM
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These LEDs came with a resistor to plug in. So you could choose to use it or not. This was in parallel with the LED. I used them but really they are only to fool the ECU into thinking that the circuit is loaded with a filament bulb.
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