LED rear lights problem

[sync24]

Hi I fitted a set of these today to my RS4 Avant.

http://www.carparts-tuning.co.uk/en/Lig ... l%20lights

They are the dogs doodahs and look very smart. They have LED Brake/fog lights but rely on ordinary bulbs for indicator/reverse lights. So that I can go completely LED at the rear I also ordered a set of canbus rear LED indicator/Reverse bulbs from mylitco (via eBay) - The LED tail light kit comes with a resistor/driver box for the RED LEDs and to put voltage into the OEM bulb holders. When I tried to use these LEDS firstly I had a flickering problem with the indicator bulb and then when I tried the reverse LED bulb the indicator failed to light at all neither did the reverse LED bulb.

Does anyone now if this problem is due to the resistor pack? I thought that the pack would just be for the LEDs and that I could use these LED bulbs as a straight replacement? Are their any car electrical guru's here that can suggest what I could do to get these bulbs working - perhaps I should use non canbus LED bulbs?

Any help appreciated - thanks!

Kev

[MikeFish]

Did you try turning the reverse bulb around? LEDs (unlike normal car bulbs) are polarity sensitive. If you didnt try this, do back try them again and if they still don't work take them out and turn them the other way.

[sync24]

Well - I spend some time today upgrading bulbs and swapping bulbs for LED's where I could.

I was unsuccessful in using the LED bulbs with the aftermarket LED brake light units. The indicators appeared to flicker and the so did the reversing lights despite me try to swap the polarity around and testing various combinations. I attribute this to them being CANBUS safe. So I have ordered some non CANBUS versions to see if these behave differently. If these don't work then It looks like I will have to remain with STD bulbs for reverse & indicators.

Kev.

[PetrolDave]

The indicators appeared to flicker and the so did the reversing lights despite me try to swap the polarity around and testing various combinations. I attribute this to them being CANBUS safe.

They flicker because they take so little current that the bulb failure warning system thinks there's a blown bulb fitted.

[sync24]

PetrolDave - if it was a voltage issue - surely the standard bulbs would not light or is the car lighting system intelligent enough to vary voltages? Just a thought I am no car sparky!
Anyone else have any ideas? Perhaps the LED ones need additional resistors ETC?

[PetrolDave]

PetrolDave - if it was a voltage issue

When did I say it was a voltage Issue?: - I didn't, I said it's a CURRENT issue.

[F@tBoyF@t]

Didn't I read somewhere that site Sponsor Trups is very close to have a full set of fault-free bulbs/lamps for the B7 RS4?

[sync24]

Didn't I read somewhere that site sponsor Trups is very close to have a full set of fault-free bulbs/lamps for the B7 RS4?

I've got the interior kit from Trups and it's all fitted apart from 4 puddle lights that light under the door - Reasonably straight fit and does make the car a nicer place to be inside and the replacement kit looks decent enough.

Problem I have, as PetrolDave has mentioned, is that the new LED rear light clusters/OEM bulb system don't appear to provide enough current for the replacement LED indicator/reverse lights I was trying to run - They flicker in the new LED clusters [which have some sort of driver unit integrated into the circuit post OEM socket connection] but don't throw error's as far as I have seen - I've reverted back to standard bulbs for the time being until I can take advice on whether it's possible somehow to fool the bulb system into delivering more current to the LED bulbs to prevent them from flickering and without the system throwing errors. I'm trying to find a alternative solution as It would be good to completely run LED bulbs inside and out. I'm almost there, reading other sites on the internet gives hint's at others wiring in resistors to prevent flickering - but I am no sparky and this may not be the right way to go! I'm trying to track down a auto electrician for some advice.

[MikeFish]

You don't need to fool the bulb system into delivering more current, there is enough current to light the LEDs. The problem is that they need less current than conventional bulbs so the car thinks the bulbs are not working and that's when they start to flicker (I think the car is sending pulses to the bulbs to check if they are still failing or not). So the answer to this is to wire in a resistor with the LEDs. The resistor it will draw more current than the LEDs alone and if you pick the right value of resistor it will trick the car into thinking the normal bulbs are in and working as normal hence no flickering.
However, if you have bought a set of LED tail lights they should have all of this built in so they don't flicker and don't give errors so it sounds like they are faulty or something is not connected properly.

[sync24]

The LED tail lights I have provide LED brake/fog's only and have bulb holders which take normal bulbs [You lift the OEM circuit boards and install them in these aftermarket ones]

See here
1. http://www.carparts-tuning.co.uk/index. ... XLAI011001
2. http://www.carparts-tuning.co.uk/en/Lig ... l%20lights

I believe they are working as the manufacturer intended - I have gone back to them to ask about running LED indicator/reverse lamps and I am waiting on them to reply. At the moment they work just fine and I am happy with them. - I am just trying to take the installation further with a complete LED replacement at the rear.

Thanks for the info RE the resistor wired inline for the reverse/indicator LED replacements - Seems like the right way to go and what you say certainly makes sense. Now to figure out the resistor value...

[MikeFish]

Ok, I misread that and thought you were having problems with the main units too.
If its just the indicators and reverse bulbs you have a couple of options. You can buy bulbs that have resistors built in and are normally advertised as error free or can us bulbs. These in my experience are a bit hit and miss (more miss than hit). The other option is o use any led bulbs and wire in additional resistors.

[sync24]

@Mike - I see you are running LED's all round. I have tried CANBUS 'safe' LED's from 'mylitco' and these seem to be reasonable quality. However these still flicker. Is it simply a case of comparing current drawn with standard bulbs in place V non CANBUS LED bulbs and then working out the required resistor for each?

[PetrolDave]

You don't need to fool the bulb system into delivering more current, there is enough current to light the LEDs. The problem is that they need less current than conventional bulbs so the car thinks the bulbs are not working and that's when they start to flicker (I think the car is sending pulses to the bulbs to check if they are still failing or not). So the answer to this is to wire in a resistor with the LEDs. The resistor it will draw more current than the LEDs alone and if you pick the right value of resistor it will trick the car into thinking the normal bulbs are in and working as normal hence no flickering.

I gave up trying to explain that...every time I tried the misunderstanding was different

I guess as an electronics engineer for over 50 years it's so obvious to me that I can forget how complicated it can seem to people that don't understand "electrickery"

[MikeFish]

@Mike - I see you are running LED's all round. I have tried CANBUS 'safe' LED's from 'mylitco' and these seem to be reasonable quality. However these still flicker. Is it simply a case of comparing current drawn with standard bulbs in place V non CANBUS LED bulbs and then working out the required resistor for each?

My signature is not 100% correct. I have LEDs all round, including LED tailights but they are similar to yours in that the reverse and indicators are coneventional lamps. I didn't think changing these to LED would make much difference through the coloured lenses. Also, I thought having LED indicator lamps might make them flash too quickly, like they do when one of the lamps blows on older cars (I assume they do on this car too but wouldn't be surprised if the speed of flashing was controlled by some device and not dependant on lamp loading).
But you are correct, if you know the normal current draw of the lamps, and the current drawn by the LEDs, then it is simply a case of calcualting the resitor value that would make the LED and resitor combo draw the same current as the conventional lamp. However, they don't have to be non-canbus ones. The canbus ones just have a value of resistor already built in (but normally too small for Audis) so this means you will more than likely need a smaller resistor to get it to work than if using non-canbus LEDs.

[sync24]

I'll be searching out a friendly auto electrician to help me achieve this "electrickery" - will report back