****** LED number plate bulbs won't work - doing my nut!

heeman10

heeman10

Audi driver since Dec 08
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I bought a pair of these bulbs off eBay: CANBUS LED/SMD NUMBER PLATE BULBS AUDI A3 03+ on eBay (end time 12-Mar-11 10:38:47 GMT)

My old LED bulbs were throwing errors, and switching off about 2-3 seconds after coming on. I swapped them out for these new bulbs, and the new bulbs haven't ONCE illuminated. I've played with the connectors, as I had to the first time round with my first set of LED bulbs, to make sure they contacted properly inside the tailgate. I've swapped them end to end, and rotated the bulbs to make sure the heat sink can't short out on the connector tangs, and all four bulbs (two old, two new) work just fine when hooked up to my battery.

WHAT IS GOING ON?! My old bulbs won't light up now either. I disconnected the car battery for about ten seconds or so, wondering if an error needed clearing, but I'm clutching at straws now and getting flipping annoyed with it!
 
Make sure the connectors on the bulb holder arent bent and that they are making contact with the connectors inside the car whan the light is pushed back into place, mine didnt work and had to be pushed back firmly and wriggled around a bit before they worked, this was when I was just replacing a regular bulb! I bought these led's of ebay and they work in my 04 A3 with no problems: ebay Item number: 320630818716
 
Do you have some original bulbs you can try? I guess you could have accidentally blown a fuse by mistake?
 
johnnythepie - I was getting about 0.3V at the contacts...I don't trust my multimeter much, but I do appear to have power there.

locost - I've tried them in about 25 different positions in the last two days, and am aware of their fiddly awkward habits! lol The bulbs I have are working successfully for a number of forum members.

Khufu - No original bulbs unfortunately, but the LED bulbs I'm replacing used to work with the Coming Home lights for a few seconds before switching off, but that set of bulbs doesn't work either now. I hurriedly checked the fuse panel lid last night by torchlight to check the corresponding fuse, but couldn't find one listed. There was a courtesy light fuse I think, and interior lighting etc, but nothing for the number plate bulbs..and I don't have any other bulb faults around the car. I'll check the manual tomorrow to see which fuse covers the number plate bulbs.
 
I have exactly the same issue mate, not a sausage from the very same bulbs!

The LED works fine though, check them on my brothers golf!

I bought some new standard bulbs and they dont work either. I've tried messing with the contacts and still nothing.

Fuse has been ruled out as they are on the same circuit as many other things that still work

Scratching my head every day thinking about them to be honest, my next step is to buy new bulb holders.
 
Well that's just great. I've read of one or two others in similar situations over time, and you're certainly in exactly the same boat as me. Welcome to my Club of a Really Annoying Problem!

I've got continuity across the terminals of the bulb holders with the bulb in place, the bulbs work, and I appear to have voltage at the pads inside the tailgate. I'm stuck, and much like you, keep wondering how to make them work again. Does an error need clearing somewhere? I remember having strange issues fitting the first pair too...they didn't work at first, and then the standard Audi bulbs wouldn't work when I re-fitted them to troubleshoot. ****** CANBUS! What are we meant to do, hey?
 
Having the same problem...LED on the right hand side switches on for about 2 seconds before going off. The Left hand LED doesnt switch on at all. They both worked fine for about 2 weeks though..havent had a chance to fiddle about yet.
 
Try running an earth wire from your bulb to a good earth not on the tailgate
 
Bit of logic here but if the std bulbs don't work either and you have 12v input..............then the bulb is shot or you have no earth. a poor earth will possibly work for a second or two.
 
Hi All,

I have exactly the same problem on my A4, old bulbs don't work now, right hand side LED comes on eventually and left hand one has no life at all, tried in wifes merc and bulb does flash - but errors on dash.

Any ideas would be great - head scratcher!

Si
 
mcnallys said:
Hi All,


Any ideas would be great - head scratcher!

Si
Click to expand...

Stop trying to mess about with led's ?!!!! lol

The sensitivity of canbus systems seems to vary considerably from car to car particularly with regard to led's.

I have fitted sidelight led's to my 2006 sportback and the nearside one throws an error every time I first start the car in the morning. As soon as the battery voltage has increased after running for 30 seconds or so then if you turn off and on again the light works and the error disappears. It is all to do with the lower current draw of led's and the lower the battery voltage then the lower the current draw.

The control module does not have the same problem because it runs with a much lower operating voltage so it is quite capable of detecting this so-called fault even though the battery might be down slightly. Once it has detected this 'phantom fault' then it has switched off the power to that circuit and it can not be re-set until the circuit has been switched off and on again.

Suggest you remove led's and replace with standard, known working, bulbs. Remove negative battery terminal for a minute and then re-connect. Then try again. I did not need to clear any fault codes for the lights to work.

As a point of interest each side of the car is treated separately by the computer so one side could work whilst the other side doesn't ! This also applies to the fuses.
 
Bluespark - pleased to hear you have found some that work. However you don't say what year your car is.

It is clear from the dozens of threads on this subject that different cars have very different computer sensitivities.

Just because they work with your car, please do not assume that they will work with all others !

Also, as you will see from other threads, initial,cold start battery voltage makes a big difference and if it's too low the computer will switch the circuit off and throw an error.
 
hello mike, yeh my car is a 2006 2.0t and just thought i would post up some i found to work after several attempts of me buying ones that didnt! lol
 
Last edited:
Bluespark - Those are the bulbs I have!

paddy - I don't have standard bulbs to try, but the last pair of LED bulbs I had that USED to work momentarily don't work even for a second now. However, when connected to a direct 12V source, both pairs of bulbs work.
 
heeman10 said:
Bluespark - Those are the bulbs I have!

paddy - I don't have standard bulbs to try, but the last pair of LED bulbs I had that USED to work momentarily don't work even for a second now. However, when connected to a direct 12V source, both pairs of bulbs work.
Click to expand...

Hi Heeman - check out post #14 !! :ermm:
 
Its funny how trends go round...In my day it was advisable to keep your number plate lights as dim as possible as they ID your car at night should you "accidental" be doing 50mph in a 40mph zone etc.
Kids today are so honest they go out of their way to make sure they are easily identifiable :) How times change. :)
 
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heeman10 said:
Bluespark - Those are the bulbs I have!

paddy - I don't have standard bulbs to try, but the last pair of LED bulbs I had that USED to work momentarily don't work even for a second now. However, when connected to a direct 12V source, both pairs of bulbs work.
Click to expand...


My point is that if you really do have a constant 12v and you know the bulbs are ok......then it must be your earth. so take a bulb out of your tail light and try that, you only ned to hold the wires against it.
 
paddy - I read and understood your point, but have been out all day. Will see what I can do tomorrow, though we are due some rain.

I went to the trouble and expense of upgrading all six bulbs in my headlights because I really dislike yellowy lights. The standard number plate bulbs give off that same yellowy light, and the crisp white light LED bulbs throw off is much more attractive to me :)
 
The trouble is its all the canbus/CE module complications. I'd need to check wiring but are they:

A) 12v to bulb & earthed via the CE module only when its happy
or
B) supplied 12v to the bulb only when CE module is happy
 
heeman10 said:
paddy - I read and understood your point, but have been out all day. Will see what I can do tomorrow, though we are due some rain.

I went to the trouble and expense of upgrading all six bulbs in my headlights because I really dislike yellowy lights. The standard number plate bulbs give off that same yellowy light, and the crisp white light LED bulbs throw off is much more attractive to me :)
Click to expand...

I did the same but isnt the side light in the head lamp the same bulb as the plate light ? in which case there is your answer :)
 
paddy said:
I did the same but isnt the side light in the head lamp the same bulb as the plate light ? in which case there is your answer :)
Click to expand...

Don't think so mate - the sidelight bulb in my headlight is a 501w and the plate bulbs are festoons aren't they ?

Not that I've actually taken the plate lights out so could be wrong !!!lol
 
They are completely different bulbs. How on earth are you supposed to check for correct voltages when the car turns off the power supply if it's unhappy about the situation? It makes diagnosing these issues a blinking nightmare!
 
If all else fails buy a new set of bulb holders for £16 from Audi, I had the same problem with mine and LED bulbs.
 
heeman10 said:
They are completely different bulbs. How on earth are you supposed to check for correct voltages when the car turns off the power supply if it's unhappy about the situation? It makes diagnosing these issues a blinking nightmare!
Click to expand...

There is a way ! But you need a large wattage (min 5 watt ) 33-47 ohm resistor. Try 47 ohm first.

Connect the resistor across the terminals just like a bulb and switch on. The resistor will fool the computer into thinking there is a bulb in and it will not switch the circuit off. Then you can test the voltage across the terminals.

Don't leave it switched on too long and don't touch the resistor because it will get very hot !
 
I've tried fiddling about with LEDs for the number plate in my A3 after one of the old bulbs blew - regrettably now spent over 30 quid on various different types that claimed to be CANBUS error free and they still don't work. Bought a pair of brand new filament bulbs to keep me going and they don't work either. I get the annoying bulb out warning on the dash constantly. Will the error clear if I disconnect and reconnect the battery, or will I need to get it cleared with diagnostics?
 
Have you tried adding a resistor to the circuit? Did this with mine and all lights working perfect with no errors on the DIS
 
audi upgrades
I just fitted these
CANBUS LED/SMD NUMBER PLATE BULBS AUDI A3 03+ on eBay (end time 12-Mar-11 10:38:47 GMT)
which are pretty much the same as the ones on this LED NUMBER/LICENCE PLATE BULBS AUDI A3 03+ CANBUS on eBay (end time 14-Mar-11 16:20:26 GMT)
No problems at all on a 56 plate 2.0tdi and not overly bright.
if your looking for realllly bright leds then go for these Audi A3 S3 (03-08) License Number Plate LED Light Bulbs on eBay (end time 01-Mar-11 17:52:08 GMT) but you would need slightly longer screws.
 
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