KLXDAVE Posted October 31, 2007 Report Share Posted October 31, 2007 Hi there Guys and Gals.. I am in the process of changing over the A4 cabriolet rear light clusters from my standard 2004 units to the new 2007 clear type clusters. I am planning on using the original wiring looms from the 2004 clusters and modifying to the new units as the new units use a separate bulb for side light and brake light, this is not a problem. The problem comes from the fact that the new clusters only have one rear fog lamp and one rear reserve lamp. And this will cause an error message on the DIS, I have been advised that the best thing to do is have a low wattage bulb connected but hidden away on both sides, but this seams a bit bodged to me, so I am looking for any advice on how to get round this problem. Can I use a resistor instead? Can I get this part of the DIS turned off for just these lamps? Can I cross wire to the other side of the boot and use the single bulb for both sides..Etc? Any other advice how to resolve would be appreciated.. Thanks KLX P.S. Just so you know the new version of the centre brake light fits straight in, you just need to reserve the wiring. Link to comment Share on other sites More sharing options...
PetrolDave Posted October 31, 2007 Report Share Posted October 31, 2007 Fit a resistor - it's the easiest way. Link to comment Share on other sites More sharing options...
KLXDAVE Posted November 8, 2007 Author Report Share Posted November 8, 2007 Thanks for that, Do you have any idea what value, Type and size (wattage) resistor is suitable.. Regards David Link to comment Share on other sites More sharing options...
PetrolDave Posted November 9, 2007 Report Share Posted November 9, 2007 It depends on the wattage of each bulb. Start from resistor (in ohms) = 144 / Bulb rating (in watts), and resistor rating (in watts) = bulb rating (in watts). Then round up the resistor value and down the resistor rating. So for a 21W bulb replaced by a LED you would need a 10 ohm 15W resistor in parallel with the LED. Link to comment Share on other sites More sharing options...
KLXDAVE Posted November 9, 2007 Author Report Share Posted November 9, 2007 Thanks for that Dave, but would a 15W resistor be wire wound and get rather hot???? 1 is the reverse light the other is the rear fog and they are on opposite sides, I presume you could just put a 2W resistor in there if you were using a LED also as the resistor only needs to handle the LED power consumption not the Bulb consumption.....I think??? How does the DIS work, I presume it just detects an open circuit or does it also detect low power consumption as in an LED might not fool it Link to comment Share on other sites More sharing options...
PetrolDave Posted November 10, 2007 Report Share Posted November 10, 2007 The resistor goes in parallel with the LED (not in series as your 2W figure assumes) - so it dissipates the same amount of power as the original bulb did! Whether the resistor is wirewound or carbon film or WHY makes no difference - it will dissipate 15W and get hot (just like the original bulb does!). There's no way round that - you have to take the same amount of power as the original bulb did or the bulb failure warning will trigger. Period. The bulb failure warning detects the resistance to chassis - if that's too high it will show a bulb failure warning, so a LED is seen as an open circuit. Link to comment Share on other sites More sharing options...
KLXDAVE Posted November 12, 2007 Author Report Share Posted November 12, 2007 THanks Dave, apreciate your advice Link to comment Share on other sites More sharing options...
andyccr Posted November 24, 2007 Report Share Posted November 24, 2007 Did this modification months ago in the summer. I just used a 5watt bulb for the 'spare' reverse lamp and got some heat resistant tape and hid the bulb behind the cluster. No problems here at all with the bulb warning lights whatsoever. I also used the original looms and it all works fine. And yes, its strange that the new centre brake light needs the power reversing ! Link to comment Share on other sites More sharing options...
KLXDAVE Posted December 5, 2007 Author Report Share Posted December 5, 2007 maybe the best option is to just use one of the new variants of LED bulbs as they run very cool and hide it in the rear quarter and have the resister built in Link to comment Share on other sites More sharing options...
andyccr Posted December 5, 2007 Report Share Posted December 5, 2007 I've had no problems with the 5watt bulb and its been in for months now. LED bulb and resistor would work just as well, but it'll cost you more to do ! Andas you never stay in reverse that long there isn't much time for heat build up Link to comment Share on other sites More sharing options...
attie Posted June 7, 2009 Report Share Posted June 7, 2009 Did this modification months ago in the summer. I just used a 5watt bulb for the 'spare' reverse lamp and got some heat resistant tape and hid the bulb behind the cluster. No problems here at all with the bulb warning lights whatsoever.I also used the original looms and it all works fine. And yes, its strange that the new centre brake light needs the power reversing ! Hi I am new to this is I have a Audi A4 cabriolet 2005 and have just purchased some 2007 rear lights, could you pleae help firstly are they LED as I have read confliting posts on this, secondly what is the quickest and cheapest option to fit these as the only have 4 bulb holders and not five sorry to be vague, can i use the wiring loon out of the old lights, if so how do i connect to the middle one as the bulb holder is a different size an where do i put the spare bulb holder, do I need to fit resistors or can you just by the adaptor kit from KAFUTEC, also the brake light you fit in the boot how do you reverse the power, sorry I am a woman and i do know a bit about cars but this one gets me please help I am really keen to get this done ASAP thanks sue Link to comment Share on other sites More sharing options...
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