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Andyuk911

How to fit LEDs to the RS4 B7 DRLs

74 posts in this topic

After a bit of research I settled on SMT mounted LEDs.

The websites I viewed were http://www.superbrightleds.com/ and http://www.v-leds.com I bought from V-Leds as they were cheaper and more importantly had what I wanted

What arrived , took 9 days to arrive from US, had a customs charge of £12 that the postoffice failed to ask for, so a bit of a result beerchug.gif

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The car before, horid yellow ...

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I decided to see if the DRL Lights were monitored by the car, so I fitted the LEDs WITHOUT the resistor. That appears to be a mistake.

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Left hand side removed

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You will then see the cap to remove, just unclips, easy to do.

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Old bulb in place

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A twist anti clock to unlock and remove. This side is easy, nice access

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Size is about the same

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LED ready to go back in.

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LED in Place.

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Bugger me, display shows Picture038.jpg

And when running this, so that's no good, would do my head in sportifs2.gif

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So out with the resistor ....

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Note the jell silicon

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I have some very good double sided tape I use for model cars, so I thought I would give it a go..

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Drivers side is slight harder to do as the Rad pipe stops full easy access to the light

So remove the air intake, easy to do, thank Audi

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Note the Rad pipe, ugh

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Turn the bulb anti clock to release, that's my arm !

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The bulb

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Quick double check

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I put the resistor under the leading edge

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Lights off

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The LED in place

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LED on

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The end result, looks better in real life jump.gif

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Thanks for reading ... I am going to get the car reset as when i start it thinks the left bulb is gone, BUT ONLY when you start. If you hit the check button, if says all OK.

Thanks

Andy

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grin.gif looking very bright mate, top work and top guide 169144-ok.gif

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I've looked at doing something similar a few times but have been concerned by the heat off the capacitor.

I'll be very interested to hear how you get on with the setup. Let's hope these LEDs last longer than some of the other LED bulbs that have been around before.

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Its always nice seeing people doing things that I know I wouldn't have a clue doing.

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The Capacitor is a Resistor, but should be ok ... I have a 2 hour drive next week so that should be a good test. The bulb is 27 SMT leds... so not normal LEDs(no glass bubble) Should be good for 2000 Hours + All in all very easy to fit... I might see Daz later today so I will take some pixs next to his car.

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oops yep meant resistor and not capacitor. blush.gif

I like the look and also the fact that you can be our guinea pig grin.gif

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I going to get some too. How much were they all incl?

Also if you need someone with VAGCOM to reset/clear that fault code, just give me shout. (Always in/around Kent).

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[ QUOTE ]

I going to get some too. How much were they all incl?

Also if you need someone with VAGCOM to reset/clear that fault code, just give me shout. (Always in/around Kent).

[/ QUOTE ]

Under £30 all in ..

Thanks for the VAGCOM offer, I'll see if Daz is in today, if not I will send you a PM

John - 21watt the original bulb.

I followed a mate in a Van past a Scammer van on the A21 ... he said the LEDs really show up nice.

The resistors do get hot, but not more than the rest of then engine bay.

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Little update.

popped to Daz to plug in the VAGCOM.

Well no fault found or recorded.

So when I arrived home I put back in the 21w bulb and bingo.. On start up it now say the RIGHT headlight is not working.

So the car is very clever to know if a bulb is there or not.

So you can either start with DRL off, OR just start see the message which disappears almost immediately.

I am happy to see the message because the car is so cool with the LEDs. The resistor is totally necessary, otherwise the bulb out icon stays.

PIX of me and DAz,with DRLs on BTW thanks Daz for the help smile.gif

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A further twist .. at night, if you leave the lights on auto, the main dipped beam comes on immediately, however, if DRL is on, the bulb icon does not go out .....

But if you turn your lights to OFF, so the DRL come on at night the bulb out icon goes immediately.

So to conclude, I think the resistor is not 100% correct. So I need to check the current the bulb pulls and then work out a new resistor.

So we need to do a bit of

Ohm's law

Ohm's law predicts the current in an (ideal) resistor (or other ohmic device) to be applied voltage divided by resistance:

I = V/R

where

I is the current, measured in amperes

V is the potential difference measured in volts

R is the resistance measured in ohms

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That looks good. Any night time shots?

Am looking to do this on my S3 as DRLs look horrid in yellow.

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[ QUOTE ]

So to conclude, I think the resistor is not 100% correct. So I need to check the current the bulb pulls and then work out a new resistor.

So we need to do a bit of

Ohm's law

Ohm's law predicts the current in an (ideal) resistor (or other ohmic device) to be applied voltage divided by resistance:

I = V/R

where

I is the current, measured in amperes

V is the potential difference measured in volts

R is the resistance measured in ohms

[/ QUOTE ]

The best way to do this is to measure the current taken by the old filament bulb, and subtract the measured current taken by the LED replacement, then use ohms law to work out the resistor value.

You normally cannot measure the resistance of the LEDs using an ohm meter as they are semiconductors.

Also, you cannot measure the resistance of a filament bulb accurately because the resistance will increase as the filament heats up.

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Not a lot of point as the DRLs are for day time and are off at night confused.gif

[ QUOTE ]

That looks good. Any night time shots?

Am looking to do this on my S3 as DRLs look horrid in yellow.

[/ QUOTE ]

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Rupert, I am now actually thinking the Audi check system on startup is smart and know that it is not a bulb ... It may send a pulse to check... I don't think a resistor can fool it .. but once running is happy to see the load.

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[ QUOTE ]

Rupert, I am now actually thinking the Audi check system on startup is smart and know that it is not a bulb ... It may send a pulse to check... I don't think a resistor can fool it .. but once running is happy to see the load.

[/ QUOTE ]

That sounds very plausable, I had forgotten that the check is done even when the lights are off. So possibly a low voltage pulse, if it's less than the LED switch-on voltage then it will see an open-circuit.

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[ QUOTE ]

Not a lot of point as the DRLs are for day time and are off at night confused.gif

[ QUOTE ]

That looks good. Any night time shots?

Am looking to do this on my S3 as DRLs look horrid in yellow.

[/ QUOTE ]

[/ QUOTE ]

Yes, but wanted to gauge how bright they were.

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[ QUOTE ]

[ QUOTE ]

Rupert, I am now actually thinking the Audi check system on startup is smart and know that it is not a bulb ... It may send a pulse to check... I don't think a resistor can fool it .. but once running is happy to see the load.

[/ QUOTE ]

That sounds very plausable, I had forgotten that the check is done even when the lights are off. So possibly a low voltage pulse, if it's less than the LED switch-on voltage then it will see an open-circuit.

[/ QUOTE ]

I thought the bulb-check worked on resistance. Even an unlit bulb would provide enough resistance to confirm a closed circuit, no?

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It must work on resistance, but you can't measure resistance without applying a voltage. Hence the low voltage pulse idea. (Not enough to light the bulb, but just enough to check it's not open or closed circuit).

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[ QUOTE ]

Hence the low voltage pulse idea. (Not enough to light the bulb, but just enough to check it's not open or closed circuit).

[/ QUOTE ]

Sounds reasonable to me - and if the voltage was below the threshold voltage of the LEDs they will appear to be an open circuit and hence appear open circuit ....but, the resistor (which should be wired in parallel) is not voltage sensitive so it would still operate.

Maybe you need a lower value resistor?

A 21W bulb will draw 1.75A (P=IV) when at operating temperature, which is equivalent to a 6 ohm resistor (R=V/I) (if the LEDs took no current). I notice from the pictures that you have a 25 ohm resistor which will only draw 0.5A so unless the LEDs draw 1.25A when illuminated your resistor is too high a value.

To calculate the correct resistor value subtract the current the LEDs are rated at from 1.75A (let's say the LEDs draw 0.5A so that would be 1.25A), and divide that into 12V (giving approx 10 ohms).

I'll take my electronics engineers hat off now (been designing electronics as my job for over 30 years)...

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Dave, that sounds very logical .. I think the SMT LEDs are very low current.. i'll see if I can find.

Any idea if Maplins or RS have resistor that would be closer

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