# LED weirdness



## episteme (Mar 30, 2006)

So, my replacement LED interior lights are in place and very nice and white they look too  Thanks to YELLOW_TT and XTR for their help in finding the correct LEDs.

One small problem however... Unlock the car, on they come. Open the door, on they come. Lock the car, down they fade. Luverly stuff. (Not my words, the words of shakin' stevens) However, when the ignition is engaged, and you try and switch the main or map reading lights on, they just kind of visually "fizzle", flickering at very low level. Annoying.com to say the least.

Any ideas anyone :?


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## was (Mar 24, 2003)

is it the same with the engine running?

your battery supply voltage might have dropped with just the ignition on.


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## episteme (Mar 30, 2006)

was said:


> is it the same with the engine running?
> 
> your battery supply voltage might have dropped with just the ignition on.


Yeah that was my first thought but, it's the same with engine running, and with exterior lights on or off. It's really odd. The only difference i can think is that when the lights are brought on automatically, it brings on all 3 at once. I've only tried switching on the main light and one map reader independently. Hang on, let me go try all 3 at once...

[Edit]: Right, I can switch one or both map readers on (but barely light up) and if i switch the main light on (barely lights) , it turns off both the map readers. Dunno if that helps any ideas...


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## John-H (Jul 13, 2005)

Do these LEDs have rectifiers within to ensure the polarity doesn't matter?

If they're wired up correctly the only other thing I can think it can be is the LED load is much less than the bulbs they replaced and might need a parallel dummy load resistor to ensure identical operation. I would have thought the fade out would be the problem here.


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## was (Mar 24, 2003)

have they always been like this?

could be that they have a very narrow operating voltage range :?


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## episteme (Mar 30, 2006)

John-H said:


> Do these LEDs have rectifiers within to ensure the polarity doesn't matter?
> 
> If they're wired up correctly the only other thing I can think it can be is the LED load is much less than the bulbs they replaced and might need a parallel dummy load resistor to ensure identical operation. I would have thought the fade out would be the problem here.


Well, I ordered the reverse polarity versions (i assume that's what you mean) for the map readers (as advised) of course I've no guarantee they actually ARE reverse polarity as they look pretty identical to my sidelight replacements :lol: - The fade out works fine...


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## episteme (Mar 30, 2006)

was said:


> have they always been like this?
> 
> could be that they have a very narrow operating voltage range :?


The OEM bulbs worked fine  No idea about the voltage range.. the LEDs in question are:

http://www.ultraleds.co.uk/product_info ... ts_id=1387 and

http://www.ultraleds.co.uk/product_info ... 4eca8c4b0b

Does that help?


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## YELLOW_TT (Feb 25, 2004)

episteme said:


> So, my replacement LED interior lights are in place and very nice and white they look too  Thanks to YELLOW_TT and XTR for their help in finding the correct LEDs.
> 
> One small problem however... Unlock the car, on they come. Open the door, on they come. Lock the car, down they fade. Luverly stuff. (Not my words, the words of shakin' stevens) However, when the ignition is engaged, and you try and switch the main or map reading lights on, they just kind of visually "fizzle", flickering at very low level. Annoying.com to say the least.
> 
> Any ideas anyone :?


Just noticed today that mine ( TTR only has the map lights no center light ) are doing the same :?


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## episteme (Mar 30, 2006)

YELLOW_TT said:


> episteme said:
> 
> 
> > So, my replacement LED interior lights are in place and very nice and white they look too  Thanks to YELLOW_TT and XTR for their help in finding the correct LEDs.
> ...


Well in some ways im glad as at least it's a LED problem, not a uh, me, problem. Well that kind of sucks, doesn't it? If anyone has any technical ideas of what might cause this, id appreciate it, as then i could raise it with Rob @ Ultraleds.

Cheers guys


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## YELLOW_TT (Feb 25, 2004)

I will be ringing them in the morning I will tell them that there are a few of us with this problem


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## YELLOW_TT (Feb 25, 2004)

Forgot to say I also replaced the center and map lights in the Golf ( the map lights are different) and all 3 work fine :?


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## episteme (Mar 30, 2006)

YELLOW_TT said:


> I will be ringing them in the morning I will tell them that there are a few of us with this problem


Ah ok Andy, good stuff. If it's ok, would you let me know what he says? PM or something? Cheers, Jamie.


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## YELLOW_TT (Feb 25, 2004)

episteme said:


> YELLOW_TT said:
> 
> 
> > I will be ringing them in the morning I will tell them that there are a few of us with this problem
> ...


Yep I will did you see my post about fitting them to the Golf :?:


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## episteme (Mar 30, 2006)

YELLOW_TT said:


> episteme said:
> 
> 
> > YELLOW_TT said:
> ...


No.... Linkage?


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## YELLOW_TT (Feb 25, 2004)

episteme said:


> YELLOW_TT said:
> 
> 
> > episteme said:
> ...


It is at the top of this page


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## episteme (Mar 30, 2006)

YELLOW_TT said:


> episteme said:
> 
> 
> > YELLOW_TT said:
> ...


I can't see it...where??   :lol:


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## robokn (Feb 21, 2006)

I have this also inmy roadster just assumed it was something to do with the alarm and the ICE whn it was fitter


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## episteme (Mar 30, 2006)

robokn said:


> I have this also inmy roadster just assumed it was something to do with the alarm and the ICE whn it was fitter


hmm...you have LEDs?


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## dannys1 (Oct 27, 2006)

I might add my OEM bulbs do this too. They come on fine, but with the engine running they do dip down and flicker slightly...this maybe affects LEDs more? Its as if the central light system is the least priorty of the electrics in the TT maybe?


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## episteme (Mar 30, 2006)

dannys1 said:


> I might add my OEM bulbs do this too. They come on fine, but with the engine running they do dip down and flicker slightly...this maybe affects LEDs more? Its as if the central light system is the least priorty of the electrics in the TT maybe?


Hmm, interesting... I'd never noticed this myself, but then I can count the times I've used the interior lights with the engine running on one...finger :lol: - I'm seeing Wak on Sunday anyway, I'll ask him if he has any ideas...


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## YELLOW_TT (Feb 25, 2004)

I rang them yesterday they said it must have some think to do with the way they are wired in the TT ( as I said they work fine in the Golf ) :? great help  let me know what wak say m8


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## episteme (Mar 30, 2006)

YELLOW_TT said:


> I rang them yesterday they said it must have some think to do with the way they are wired in the TT ( as I said they work fine in the Golf ) :? great help  let me know what wak say m8


Certainly will, cheers.


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## John-H (Jul 13, 2005)

I measured my standard bulbs before briefly and can confirm that the voltage for the two map lights is reversed i.e. positive for the body, negative for the end - and the polarity doesn't reverse when you open the door, turn on the light manually or turn on the ignition. Might do some more tests later.

So, is it both the main festoon AND the map lights that all flicker or just one or the other - when the ignition is on and you press the light switch?


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## XTR (Mar 2, 2006)

Sunviser's flicker too.


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## John-H (Jul 13, 2005)

When you say they "flicker at a very low level" do you mean they are almost extinguished but give out a little light in short flashes - or - do you mean they are still fully on but have tiny off moments?

I've noticed the standard ones are brighter when the switch is operated than when the door is opened. That's because the door opening is controlled by a transistor whereas the mechanical switch is direct.


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## episteme (Mar 30, 2006)

John-H said:


> When you say they "flicker at a very low level" do you mean they are almost extinguished but give out a little light in short flashes - or - do you mean they are still fully on but have tiny off moments?
> 
> I've noticed the standard ones are brighter when the switch is operated than when the door is opened. That's because the door opening is controlled by a transistor whereas the mechanical switch is direct.


In terms of flickering, yes that's exactly what they do - almost extinguished but give out little flashes.

Interesting what you say about the transistor - that would explain why they work ok (fading in/out as part of the unlock/lock process) from the fob as well then... But why would the direct method make a difference? :? It's really odd...


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## John-H (Jul 13, 2005)

episteme said:


> John-H said:
> 
> 
> > When you say they "flicker at a very low level" do you mean they are almost extinguished but give out a little light in short flashes - or - do you mean they are still fully on but have tiny off moments?
> ...


The central locking controller controls the dimming process when the centre switch is in the middle (between "0" and "1") position.

I had a look at the wiring diagram and it seems that with the centre switch switched to "1", for the lights to be on permanently, what I had presumed was a direct connection to the 12V+ve rail is in fact a +ve rail controled by the central locking controller. This same rail is also used as a +ve rail for the sun visor lights. So there is scope for this rail being switched on and off by the control module!

Actually this would make sense because if the lights were left on ("1" position) and the car locked, you'd want the lights automatically switching off to save the battery. The manual also says a similar thing happens after four minutes if you leave the door open.

Unfortunately I don't have internal details of the central locking controller. I'm guessing, however, that there may be some sort of sensing function, where the +ve rail is briefly set to 12V to test if there is a load. I'm not sure why this would be necessary but I think the loading issue is the key to this problem as the only difference is that the LEDs are a much lighter load.

The solution would be to add a dummy load resistor across each bulb. It would be easy to solder one across the festoon bulb but the two map reading bulbs would be tricky. For these it would be best to add resistors to the back of the light housing I think. Not sure what value they should be as you don't want them getting too hot.

A 200 ohm resistor would dissipate 0.7W at 12V and 1W at 14V and take 3 times the power of the LED bulb (20mA x 12V) and might be enough to get over the problem. Trouble is the standard bulb takes about 5 times as much again. If more load is needed the resistor would need to be physically larger.

If I get time today (doing an oil change service) I'll try and find out what works.


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## John-H (Jul 13, 2005)

Pulling out the key will turn OFF the light, even if the light switch is ON. Turning ON the ignition immediately restores the power again.

I didn't manage to have much of a look yesterday but I did discover that if you accidentally short out the +ve rail from the central locking controller  , it doesn't blow a fuse but removes the power for a while. Clever :wink: .

The more I think of it the more it seems that the current is being monitored by the pulsing seen with the LEDs when the ignition is ON. If a pulse draws enough current it turns on the power continuously. Quite why it doesn't just turn on the power continuously in the first place I'm not sure :roll: . There must be some reason for it. Anyway...

I'm going to order some Ultraleds LED lamps tonight. When I get them I'll find out what resistors you need to add to stop the flashing. I'll let you know.


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## episteme (Mar 30, 2006)

John-H said:


> Pulling out the key will turn OFF the light, even if the light switch is ON. Turning ON the ignition immediately restores the power again.
> 
> I didn't manage to have much of a look yesterday but I did discover that if you accidentally short out the +ve rail from the central locking controller  , it doesn't blow a fuse but removes the power for a while. Clever :wink: .
> 
> ...


Blimey, current monitoring? Seems a tad elaborate!! Why would you... ok you've already asked yourself that :lol: If you do end up ordering them and having a play, I'd be very interested to know what happens.

Cheers, Jamie


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## John-H (Jul 13, 2005)

Just ordered them a few minutes ago. Will take a few days... I'll let you know.


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## John-H (Jul 13, 2005)

I received the LED lights very quickly (yesterday) from Ultraleds and installed them today.

They are very bright - a vast improvement on the filament bulbs. The 6-LED festoon bulb is made up of six square domed quad LEDs similar to this one from http://www.besthongkong.com.









http://www.besthongkong.com/high-power- ... pick-color

In fact the 3 LED version in the Ultraleds lamp means it has 18 LEDs in operation! The light output is very evenly spread from these devices with 100 degree wide angle viewing. In fact I had already purchased a few separately, with a view to making this lighting mod myself but I'm glad Ultraleds saved me the bother  . The single versions I obtained are rated at 80mA per device (4 x 20mA) and the Ultraleds design operates at 60mA for each device, with two parallel chains each of three in series, so 120mA in total - they should last for a long time as they are not being overdriven and the device is designed to be direct mounted on a PCB, so there should be no thermal damage from the manufacturer's soldering process.










EDIT NOTE: Above product discontinued. Nearest equivalent is this one:









U426UCW http://www.ultraleds.co.uk/264-42mm-6-w ... white.html

Or this one can also be squeezed in and gives a brighter light:









UCW429 http://www.ultraleds.co.uk/264-42mm-9-w ... white.html

This one has an in-built resistor which avoids adding one as detailed below but is not as bright as the 9 lamp one above:









U428ACB http://www.ultraleds.co.uk/264-42mm-8-l ... rning.html

The above festoon lamp can be connected either way round as it includes a bridge rectifier to ensure current flows the correct way through the LEDs.

*NOTE: The two map lamps are REVERSE POLARITY *i.e. side is +ve and end centre contact is -ve (not the same as the sidelights - Not the normal way round!).
Although I've not tested this myself, it seems that the Roadster's different lampholder is the opposite polarity i.e. centre end contact +ve and side -ve. For this you'll need the standard polarity (end +ve) - both are BA9S fitting lamps
(BA = bayonet, 9 mm diameter, S = single end contact) with bayonet pins opposite at 180°.

These lamps are a possibility from an alternative supplier as they are non-polar:

http://www.wardenjp.com/stores/ba9s.html










*Flickering Problem*

Anyway, to the problem; I can confirm that mine flicker too, when the light switch is operated, regardless of whether the ignition is on or off. Opening the door or removing the ignition key operates them correctly at full brightness.

I had thought that there was, in effect at least, some form of load sensing of the lamps by the TT's central locking controller and this was confirmed. Quite why it needs to do this I'm not sure.

With the lamps flickering, connecting a 100nF capacitor across them stops the flickering, proving this was AC fast pulsing in nature, with effectively a low voltage - but of course no DC current flows through the capacitor :wink: . Connecting a resistor across the the lamp causes them to operate at full brightness due to the DC current draw  - i.e. the controller senses the load correctly and turns on the power. I think that the problem may be that the LED lamps do not take much current until there is at least about 3V across each LED and the sensing does not reach this level. Adding the resistor allows the sensing circuit to detect a current draw at a lower voltage, so the light comes on :idea: .

I tried a few different values of resistor and could get it to work properly with 500 ohms or less. I chose a value of 330 Ohms, so as not to draw too much power. 12V with 330 Ohms draws 36mA, so not much on top of the festoon lamp's 120mA. Worst case dissipation might be 14.5V^2 / 330 = 0.64Watts. To keep the temperature low I used a 2Watt resistor. This is very conservatively rated and runs cool.

The resistor can simply be soldered across the festoon lamp's connections. I used some heatshrink tubing to insulate and protect the resistor body. Sorry about the fuzzy pictures  but you get the idea.


























In hindsight I think I should have soldered the resistor on the inside of the end caps as the TT's lamp holder can catch on the solder joints. It's not a problem though and makes it less likely to rotate.

One word of warning. Soldering the endcaps can melt the solder joints to the LED circuit board and cause the endcap to move. Lightly abrade the endcap first, where you want to solder it and be quick to solder and use a powerful soldering iron to heat up the joint area quickly. There's less chance of heating up the whole cap and loosening it this way. Holding it firmly in place will also help.

*Conclusions*

These LED lamps are excellent and provide a brilliant light. The problems with flickering when operating the switches has been overcome by adding a 330 Ohm 2W resistor across each bulb.

With only the one resistor across the festoon lamp, operating the centre switch to illuminate all three lamps works fine but without resistors across the map reading lamps, operating their own switch still results in that map light flickering.

Adding the resistor directly to the festoon lamp is relatively straight forward but adding resistors to the map reading lamps is not, due to their compact size. This could perhaps be better achieved by adding the resistor behind the lamp holder. I'll look into this and the possibility of modifying the map lamps.

With all three resistors added, one to each lamp, there is no more flickering from any lamp.

*ADDENDUM:*

Any problems with radio interference after installing some types of LED lamps (not the above - but ones with switching regulators inside) then see the following: http://www.********.co.uk/forum/viewtop ... 6#p1377596


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## episteme (Mar 30, 2006)

Hi John

Firstly thanks for all your work on this (or more to the point, reporting your work on this ) - it's really very helpful.

Everything said makes sense but I, like you, would be interested in knowing the reason for the load sensing circuit... causes a lot of bother!

I shall dig out my soldering iron and a resistor and apply said change. I think ill just live sans map readers as I've never used them anyway. Not the perfect solution, I know, but a lot easier than soldering resistors to the back of the housing :?

Anyway, thanks again for the information.

Jamie


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## John-H (Jul 13, 2005)

No problem Jamie - I'm glad I got spurred into making the mod too as it's much brighter [smiley=sunny.gif] .


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## gadgetboy38 (Mar 9, 2005)

i have a slightly different led
http://www.ultraleds.co.uk/product_info ... ts_id=1119
do u think that the resistor that you have chosen would be ok with this l.e.d.

Also i want to add the resistors to the map lights but cant work out how to remove the unit does anyone know how this is done?

thanks for your help.


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## John-H (Jul 13, 2005)

The resistor works in tandem with the current sensing in the central locking controller so it should work with any LED lamp - or no lamp - but then you wouldn't see anything but the voltage would be there :wink:

I can't see how to remove the lamp holder in Bentley. I'll have a look later myself.


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## gadgetboy38 (Mar 9, 2005)

followed your instructions to the book and it works perfectly and you dont even need a resistor over the map led lights they seem to work perfectly now i just have to replace the vanity mirror lights and that will finish it off perfectly.

thanks for all your help John couldn't of done it with out your help.

one thing to add if anyone decides to use ultra l.e.d lights for their numberplates DONT they only seem to last a few hunder hours at most i have installed VARAD ones so far they have out lasted anything alse ive tried.

http://www.ragingspeed.co.uk/catalog/pr ... cts_id=143


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## episteme (Mar 30, 2006)

Welp, just soldered the resistor on to the festoon and I'm pleased to report it all works perfectly 

For anyone else solving the flickering problem this way, I can confirm (as gadget boy said) that the single resistor across the festoon contacts also fixes the map readers.

John, thanks again for the fix for this, very much appreciated. Katie has also told me to thank you because, and I quote "oooh, now your lighty :roll: things work, you can wave to me from your car at night when you drop me off." Sigh. Up until now, I'd been using the "oh, the interior lights dont work properly" to save that embarrassing task  Now I have no excuse!


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## John-H (Jul 13, 2005)

:lol: No problem. Although I think you'll find that although the map reading lights light up with the main light with the big switch, if you try to turn them on independently, with the ignition on, you'll still get the flickering on that particular map light. They each need the resistor load. If you never use them independently it's not a problem.


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## gadgetboy38 (Mar 9, 2005)

well it did work for a bit then it they started flicking again so ended up soldiering resistors over the map lights also, if anyone wants some picks let me know with your email address and ill send you some so u can see how i did it. and since i had the thing apart i decided it add lights too the foot wells (let their be light)


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## episteme (Mar 30, 2006)

John-H said:


> :lol: No problem. Although I think you'll find that although the map reading lights light up with the main light with the big switch, if you try to turn them on independently, with the ignition on, you'll still get the flickering on that particular map light. They each need the resistor load. If you never use them independently it's not a problem.


Ah, yes, with the ignition on the map readers still flicker.  Well, if I get really bored one afternoon...


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## episteme (Mar 30, 2006)

gadgetboy38 said:


> well it did work for a bit then it they started flicking again so ended up soldiering resistors over the map lights also, if anyone wants some picks let me know with your email address and ill send you some so u can see how i did it. and since i had the thing apart i decided it add lights too the foot wells (let their be light)


Hmm...interesting. If you don't mind ill take you up on the offer of the pics...ill pm you my email address (if you pics for the footwells that would be great also) Jeez, this is turning into obsession :lol:


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## gadgetboy38 (Mar 9, 2005)

tell me about it just got some cheap cold cathodes in at the moment but want some of these eventually,http://www.litewave.co.uk/iceled_tube.asp look for the videos.


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## John-H (Jul 13, 2005)

gadgetboy38 said:


> well it did work for a bit then it they started flicking again so ended up soldiering resistors over the map lights also, if anyone wants some picks let me know with your email address and ill send you some so u can see how i did it. and since i had the thing apart i decided it add lights too the foot wells (let their be light)


You used a 330 Ohm resistor across the festoon and the festoon flickered? Are you sure one of the solder joints hasn't come off? The endcaps can be tricky to solder and get the solder to flow and wet the surface. With that sort of metal you often need to scrape it first. The solder can sometimes look OK but it's only held on with flux.


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## gadgetboy38 (Mar 9, 2005)

yeah its all sorted now cheers john


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## dannys1 (Oct 27, 2006)

I know this thread is a little old but a question and an idea came out of this...

First the question - I assume with the this trick fitted to stop the bulbs flickering, it also stops the fade out after you've shut the doors?

Now the idea...

A while ago i was chatting to a few members about what the new audi's do - when you unlock the door with the keyfob it turns the fog lights on (like it does the interior lights) and they fade away when you get in.

Wak has set up something similar on his car to happen with his angel eyes.

What i thought might be quite good is to wire down from the interior light to the engine bay and connect up to the fog lights so that the same thing happend as with the new Audis - the problem with this being that everytime you turned the interior lights on by the switch, your fog lights would come on too. BUT if as you say when you press the switch a lesser voltage is induced, wouldn't it be possible to have a relay set up that would only open and send the voltage through to the fog lights when it was full (eg when you opened doors, unlocked car etc)

What are your thoughts John?

- Danny


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## John-H (Jul 13, 2005)

Hi Danny, all the best threads are odd :wink: .

Firstly, the LED lights still fade out nicely, albeit with a slight difference - whereas before they faded 10,9,8,7,6,5,4,3,2,1,0 , as it where, they now fade 10,9,8,7,6,5,4,3,2,0,0 - the tail end is slightly abrupt because the LED lamps do not have a linear characteristic at low voltage. Perfectly acceptable though.

I'm not sure what you mean by lesser voltage but anything is possible with enough engineering effort. It might be possible to use the switch in the light as a logical routing of the feed with the aid of a relay, so when the switch is set to ON, the relay does not power the Fog ligts from the interior light feed - but when the switch is set to centre position it does allow power through. There is one thing that might scupper the use of the interior fader though - it might not handle the power of the Fog lights and you don't want to blow the controller :?


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## dannys1 (Oct 27, 2006)

Ah yes, of course using the switch would be another way. To stop it blowing the controller you could just use another relay and a power feed from the busbar couldn't you?


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## John-H (Jul 13, 2005)

You want it to fade though so the power would need to come through the controller where the "dimmer switch" is. There are other ways with transistor followers but then you might as well make your own dimmer.


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## dannys1 (Oct 27, 2006)

Oh yeah very good point - do you think it can be done this way?

Its a very subtle mod and quite a bit of work to do it, but it would be a great way to update the MK1 tt some more (i imagine the MK2 TT's do this, its standard on all Audi's now isn't it?)


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## Black Knight (Jan 16, 2007)

I saw a new merc C class. turns on and keeps fog lights on for like half a minute after locking.. follow me home thing i guess..


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## gadgetboy38 (Mar 9, 2005)

Black Knight said:


> I saw a new merc C class. turns on and keeps fog lights on for like half a minute after locking.. follow me home thing i guess..


That also happens on merc's when you unlock the car but it only works at night.


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## Simpson. (Nov 7, 2010)

Just trying to make sense of this thread... as i have a Roadster, So only have the 2 map lights (BAS() and not the central light as the coupes do (Festoon bulb)

Your photo's only show fixing resistors to the main festoon bulb.

...What do you need to do if you just have the 2 map lights like a Roadster?..Im fed up of orange lights in the cabin 

Anyone..?


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## Simpson. (Nov 7, 2010)

Ive got the bulbs, and also asked this question afew months ago.

You need to fit some resistors across the back of the bulb terminals.

Do a search on here, there is a thread somewere (for a coupe) but same thing has been done.

I havnt fited resistors to mine yet.


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## mullum (Sep 16, 2011)

As fitting resistors is both inconvenient and potentially dangerous* - I've had coupe map lights custom made. No bulbs which work correctly are available off the shelf. See listings in the marketplace :

*if standard bulbs are fitted after fitting resistors, the resistors will burn and could cause a fire! Do not solder in resistors, this is very poor practice. Especially when bulbs are now available


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