S6 C6 only 2 out 5 DRL LEDs light up

[ricxk916]

If you like a puzzle then you'll LOVE this. I will be amazed if anyone knows why this is happening.

On my 2006 S6 C6 the right DRL only lights 2 of it's 5 LEDs.

Put the left DRL on the right hand plug and all 5 LEDs light.

Put the right DRL on the left hand plug and only 2 LEDs light.

"EASY it's a fault on the left DRL!" EXCEPT remove it and test it directly on a 12V battery and it lights all 5 LEDs.
(There are 3 pins on the DRL. Positive, ground and 'control'; where 'control' (I believe) is a signal line from a module to tell the DRL to dim itself. All 5 LEDs light whether 12V are fed just to positive or to positive and 'control')

Any ideas? Thx.

[Crasher]

Private message me the cars reg number please.

[dan2485]

If you like a puzzle then you'll LOVE this. I will be amazed if anyone knows why this is happening.

On my 2006 S6 C6 the right DRL only lights 2 of it's 5 LEDs.

Put the left DRL on the right hand plug and all 5 LEDs light.

Put the right DRL on the left hand plug and only 2 LEDs light.

"EASY it's a fault on the left DRL!" EXCEPT remove it and test it directly on a 12V battery and it lights all 5 LEDs.
(There are 3 pins on the DRL. Positive, ground and 'control'; where 'control' (I believe) is a signal line from a module to tell the DRL to dim itself. All 5 LEDs light whether 12V are fed just to positive or to positive and 'control')

Any ideas? Thx.

You got yourself muddled there, do you not mean that the right hand DRL has fault within it.

The control line is a LINBUS signal, as I read it the signal wire/connection within the DRL is corrupting the operation of the LED's as you have proved that the car is good by using the other sides DRL in the right hand position.

Have you had any water ingress in the DRL as this could have put corrosion on the wiring connections causing tracking and the lighting of 2 LED's only? When the wire is disconnected the LED's work as they should as you proved with the bench test.

One option that you could try is to remove the signal wire pin from the connector on the car and test it to see if the 5 LED's light up.

If they do then the DRL needs to be replaced or opened up and checked.

[ricxk916]

Wow Dan, thanks! Correct on every point.

I did mean it's a fault on the right DRL.

I have fixed a CANBUS issue before but I was ignorant about LINBUS, so I've Youtube'd up and understand there will be a LINBUS slave module within the DRL itself that is corrupting the signal from the master module. Looks like if I had an oscilloscope (or 'PicoScope' a guy uses on Youtube) I would be able to confirm the signal being sent on pin 2 of the plug; but I don't.

As the DRLs are stupidly expensive it makes sense to at least open it up and see if the slave module can be identified and repaired. I have fixed electronics in the past that just had a 'dry joint'. Fingers crossed.

There is no evidence of water ingress. The lens isn't even cracked; miraculously given where it lives.

I will post an update.

Thx, Ric.
06 S6 C6 4F5

[swalker]

You stuck 12V on and all worked - but as i am sure you have seen on top gear that lights flash on camera, to dim they dont add a resistor or turn down the voltage they pulse a signal at it, but it is that quick the naked eye doesn't catch it we just see a dim light. eyes only work at 80Hz
so sticking the 12V on solid is like punching it, therefore i am going with dry joint or poor IMC - same thing just not visible, not letting the signal through. take her apart and reflow. Fingers crossed.

DIY Scopes can be picked up for cheep the pico scope is not a scope - they will say that themselves - yes it captures signals but if you use a scope day in day out you cant just pick up a pico and run with it - there is a learning curve as it uses an app.
you can pick a scope ( think thats what this is) for dirt cheap, KKmoon DSO138 2.4 inch TFT Handheld Digital Pocket Oscilloscope Kit SMD Soldered + Acrylic DIY CASE Cover Shell for DSO138: Amazon.co.uk: DIY & Tools < wouldn't use it for ultimate measurement.

[ricxk916]

Thx Stewart. I saw the square wave on a LINBUS Youtube tutorial but I hadn't clicked on the signal pulsing to dim the light. I would love to get into the unit and at least try to reflow the solder BUT I have tried baking it in the oven (100C) to soften the 'glue' with no effect. It looks like a plastic weld to me between the back of the lens and the carrier. I have also had a go with my Dremmel but it would take considerable damage and time to get the unit open. So, I'm probably going to shell out for a replacement. But at least I learned a bit along the way.

Thx, Ric.
06 S6 C6 4F5

[Crasher]

Headlight part number 4F0 941 030 EF and £728.22 inc VAT.

[dan2485]

GENUINE AUDI A6 S6 05-11 LED DAYTIME RUNNING LIGHT BAR RIGHT O/S 4F0941068A | eBay