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Discussion Starter #1
To prolong the life of your aftermarket LEDs, it may be worth switching off the "cold diagnostics" of the lamps you have replaced. You may notice that the lamps flash a few times when you switch the ignition on. Some people on the internet reckon that some LEDs don't take too kindly to this, and they're probably right.

You can switch off the cold diagnostics in the long coding of the Central Electronics module (09) using VCDS or OBDeleven.

Be aware that this is not the same as disabling bulb monitoring and will not fix bulb out warnings on LED units that don't have sufficient resistance - the only fix for that is to add a resistor in parallel with the LED - you will find plug-and-play "CAN-bus adapters" cheaply enough on your favourite auction site.
 

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I've bought a few aftermarket led bulb replacements and run tests on them. The Chinese sell using brightness as their USP even trying to make theirs look brighter than other sellers in photos. I've dissected quite a few and whilst they may use led chips with a genuine power spec., they use lower value series resistors to increase current and do nothing about removing the heat. I've yet to find a replacement led equivalent lamp where they've considered thermal management. Their other design issue is they often design on the bench for 12 volt when all car lamps should be designed for 14.5 volts. Leds bought from genuine companies like Ring or Philips should be good, but they all find it hard to remove heat for the standard 2 wire push in base. A brass capped lamp offers more opportunity to use the the cap as a heat sink. You can sell a led replacement as 1W, 3W or 5W. They use the same leds and push more current through them with most buying the biggest number.

I've left some of these Chinese auto leds running on a bench supply for hours. Most go pop after 2-3 days on continuous test, some only lasted 3 hours. O.K that may translate to a reasonable mileage, but you get better life from a tungsten bulb. If I buy any of them I hack their resistors increasing their value to reduce current, whilst accepting a 10% reduction in brightness.

The best auto leds are those designed with constant current chips running at sensible currents with a metal body for the heat sink, they will be for larger led clusters like DRLs. Leds should not fail easily and I can't see how flashing a led causes it to fail, unless they are running too much current through the chips and peak voltage causes breakdown. My EOS like others has led clusters for the turn signals which flash often. The failure of individual leds in those is due to their highish running current to meet brightness regulations for the older version led chips, or water ingress.

You get what you pay for with Chinese led bulbs, if you buy any, connect one across your battery and leave it running to see how long the led lasts - if it starts feeling hot and hotter you might get 3 days if you are lucky!

The lamp failure test at key on flashes a led bulb because it needs far less current to see it flash than a tungsten lamp. But if it can't survive that it isn't going to last long turning the lights on and off either.
 

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Discussion Starter #3
I'm fitting some Narva LEDs to the projector lamps. They're the same as the Philips Ultinon LEDs (Narva is a brand of Lumileds, which is Philips's LED lighting joint venture); aside from showing the bulb out warning they seem to be well made - they have wire braid heatsinks and small control units so everything fits in the headlamp housing as it should. Once I get everything working the way it should I'll post more on this - of course in the UK they would only be legal if the car is fitted with headlamp washers, but they do seem very good.
 

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I think I would be confident with those. I bought a pair of Philips DRLs and was V. impressed with the solid finned ali heatsinks, although their black paint finish didn't weather well and I repainted them. The problem with bad thermal management of led designs on cars is worst when they are sitting in traffic in Summer with no airflow. Slightly off topic, I just got some cheap Chinese MR16 led replacements. Running 5W from 12V with a zillion led chips on a 50mm diameter ali pcb and no space between, they got so hot the solder connecting the supply wire to the board melted and the wire lifted off! Some of this stuff really is cr*p! I'll fix these lamps by increasing the current sense chip resistor value and dropping the output from 5W to 3 W.
 

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Discussion Starter #5
Yes, having looked around the world of cheap Chinese headlamps I realised that not only was it not possible to see through all their fake power output and lumen ratings, but even if I did find some that were actually at least as bright as halogens they would probably either not last or not fit! These should last well (at least until the next generation of LED lighting is out and I want an upgrade!), and they're designed for projector lamps. I have another LED modification I'm looking into so that I don't have to run with the new LEDs on all the time (headlamp rules over here say lights on 24/7), but I'm trying to find a DRL mode that will work on the parking light circuit with the headlamp switch in Auto... hence the thread about CECM versions!
 

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What are you doing about the other lamps? I fitted 6K HIDs on a bike but the tungsten parking lamp looked sick against it. I had to led that too to get the right look for all lamps. I ran my HIDs on low beam all the time and I'd expect to do the same with leds. Some argue different, but a 6K low beam is very visible and IMHO safer in daylight. Do a simple sum of running hours for your annual mileage at an average of 50mph and you find it takes years to burn even 6000 hours for a HID lamp. Running a led lamp continuously as a low beam is why I would fit one and if it won't do the 10-20k hours life they claim, it can't be that good?

I have a later 2012 VAG group car which to me has strange in built drls. They modulate the tungsten low beams reducing their power, but they put out an extemely yellow light. I haven't even thought about doing anything to those lights as I'd have to deal with the modulator and bulb failure monitoring.
 

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Discussion Starter #7
I just finished installing the switchback LEDs for indicators/parking lights. I'll write up how that went at some point. The front fogs are still the regular halogens, which I'm not bothered about since I seldom use them.

Regarding the DRLs, the behaviour you describe is the standard behaviour, and it's configured in the CECM (or, for a 2012, BCM - body control module) coding. Default is that DRLs are low beam with 71% brightness; you can switch the DRLs to use fogs rather than low beam, and you can switch between Scandinavian mode (all lights on) and US mode (headlights only, only on when the handbrake is off). I'm hoping that the new CECM I have on order will behave correctly with the DRL dimming and will allow an option of 0% so that my parking lights will work as DRLs. Apart from anything else, what with the resistors on the low beam and all the wiring, the headlamp housings are quite full, and avoiding the heat generated by having low beams on would probably be beneficial!
 

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Discussion Starter #8
In which aku-aku learns the lesson "don't buy cheap Chinese tat" for the 94th time...

The switchback indicator/DRL bulbs that fit in your indicators just aren't compatible with VW electrics.

There's a kind that have been around for a while now, which have a big cheap resistor and a rubber gasket to fit into the bulb housing. I tried those, and the DRLs go off after a few seconds when the engine is on. Mysteriously, with the engine off they behave just fine.

There's a new kind which fit into the bulb socket and have three thin (and presumably flimsy) wires that go out to a fancy-looking block that is presumably just a slightly fancier resistor, and a cable for the DRL input. I tried those, and the DRLs stay on correctly, but the indicators blink very briefly and sometimes flash white when the engine is on. Mysteriously, with the engine off they behave just fine.

In short: don't bother with the two kinds in the pictures. The mk5 electrics don't support them and basically don't know what LEDs are, so anything that is more complicated than just an LED will need to have been designed with the mk5 VW in mind.

That said, there's another kind which doesn't have the extra resistor box - so in a few weeks' time it'll be time for another "don't buy cheap Chinese tat" update ;)

22451
22450
 

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Its good to see somebody trying these things out and posting, even if they don't work. I've played with a couple of housed led spotlights and some mains led floods, worked out the led constant current drivers and modded their circuits. Apart from the Chinese over running them, most have the ali conducting plate of some kind with 'x' surface mounted leds. When the Chinese sell something saying it's 50W, accept and run it at 25W and it will be reliable. I'm going to experiment with a 35W H7 and try out some cooling ideas, even if it means chopping off part of the rear end. The V.W interface will come next.
 

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Discussion Starter #10
The latest package from China arrived... and I can report 50% success!

These bulbs have all the electronics built in, with one thin wire coming out that has to be squeezed through the bulb fitting. The wire is much, much thinner than in the picture, so it's not a problem fitting it - though I do worry about the insulation not being thick enough. The wires have bare ends, so I attached a spade connector to join on to the wires I'd left in from previous attempts.

Unfortunately, as you can see in this video, one of them doesn't work properly so they're sending a replacement. When that arrives, if everything works, I'll be able to give them a longer-term test.

22480
 

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Next part of my story... I tried fitting some X3 LEDs to the fog lights - they claim "no CAN-bus errors" but the bulb out warning showed up. Despite having a big heatsink, these would also fit on the main beam, so I was disappointed that they didn't work out.

This thread is quickly turning into a rogue's gallery of what not to get - I guess I'll keep it that way, and if I ever get some success I'll post a new thread with the recommendation.

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If I'm playing around with bulbs and have some spare time, I'll investigate how a tungsten bulb is seen by the system and whether it can be easily emulated electronically? Each bulb would need an external 'dongle' of some kind. I won't go down the road of padding out with high wattage resistors since it defeats the object of using leds and for the trouble you might as well stay with tungsten. Which bulb and holder is the easiest to play with? I don't fancy messing with fogs in the front bumper, been there and not so easy to remove as they say. The problem with emulation is I might fool the system to think it see a normal bulb, but it won't then tell you if the led replacement has failed, is that something you can put up with?
 

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I have some questions as I am a bit confused. What brand of light is the one that is blinking . I would hope that it is not the same as the fog light because they are different series. You may have been getting a bulb out indication because the LED bulb wasn't drawing enough current to be sensed. Did they blink when used as fog lights? I think the sensing circuits are looking for 3.5 Amps of draw or more. I haven't seen what the sensing pulse looks like If it has a positive and negative component, that may be why the regular bulb gives no error because it has no polarity issues. The LED may cause an error because it is a polarity driven device. It will only let one phase of the pulse through but not the other. The only way to solve the problems may be to disable the circuits using VCDS or similar as was mentioned previously. For the current draw problem a resistor would probably work but as Vox magma has said you aren't getting any energy savings. You could also try an LED rated at 35 watts. I am using 50 watt (each) LEDs on my high beams. I get the blinking but not the bulb out. I don't know about coding, but is the cold diagnostics causing the blinking?
 

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It can get more complicated. Many of the regular bulbs are electronically driven from PWM or d.c controllers. Bulb failure sensing might only need to catch the first few cycles of PWM at key on, or is continuously monitoring peak pulsed current rather than d.c. You would need to 'scope each bulb you were considering replacing to detect PWM or pulsed lamp testing. Once you know how they do it, you can design the electronic 'dongle'. For d.c driven lamps they could generate a short duration lamp test pulse which enables lamps to be tested when they aren't lit. That's how you could get the bulb failure warning at key on during system initialization checks.

I was experimenting with small 1W led puddle lights which would normally be 5 watt tungsten. As supplied they always put up a diagnostics error but no bulb failure. On those I could have added a fixed resistor to emulate the full 5W normal load, but it would run as hot as a lamp and would need sufficient air cooling around it. By experiment I could choose a higher resistor value which kept the led lamp current just above the diagnostics fault trip level, but you have to do this for a 9-10v system voltage simulating a low battery charge or cranking voltage drop. Otherwise, you will still trip a bulb failure diagnostics error cranking on a low battery.
 

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Discussion Starter #15
I am using 50 watt (each) LEDs on my high beams. I get the blinking but not the bulb out. I don't know about coding, but is the cold diagnostics causing the blinking?
Cold diagnostics causes the blinking, yes. All LEDs I've tried (main beam, fog, parking lights) do the blinking on ignition on.
 

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Discussion Starter #16
Which bulb and holder is the easiest to play with? I don't fancy messing with fogs in the front bumper, been there and not so easy to remove as they say.
I would say the H7s in the high beam are the easiest to get to and remove - you can probably pull the connector off the bulb without removing the bulb.

The problem with emulation is I might fool the system to think it see a normal bulb, but it won't then tell you if the led replacement has failed, is that something you can put up with?
I suspect that failing LEDs would not be reported anyway, so that's no problem for me.
 

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I replaced my parking light (The 2825 bulb inside the high beam housing) which doesn't blink as well as the dome lights above the rear view mirror with LEDs and no issues. What about a simple LC or Pi filter in series with the LED. This might strip the pulse out but not the DC to keep it running. It may not affect the current sensing function. Question is, it this feasible and what effect would it have on the system. Additionally you would need one of these filters for each light. I think changing the coding would be the best option if possible. No extra parts and likely little to no effects on the rest of the system. Also might be the best way to eliminate the bulb out error. None of this seems to affect Xenon replacements. Maybe it has to do with the ballast or because the xenon tube itself can't react as fast. Replacement Xenon kits will wire in directly where the old H7 bulb was with no errors. They do have a high in rush current when they are firing up. 35 Watt kits are around 7-8 amps and about 3-4 amps when running. Tungsten lamps have a higher current draw while running but I don't know if there is surge value. I know we are not talking about Xenons but I thought this info might be useful. One other thought. There was mention whether a dead LED would trigger the bulb out warning. I believe it would still occur unless the circuit used to detect the bulb were disabled or the bulb was by passed. A bulb that is dead (zero current draw) or pulling a current below the required amount will trigger the bulb out warning. At least That is what I am seeing in my experimenting. My logic may be flawed but these are the results I am seeing. The high and low bulbs are both H7 (at least they are in my 07).
 

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I can't be sure until I measure what they are doing but I was thinking along the lines of a low RDSon power mosfet into a low ohm resistor when lamps were off, then turn off the fet when the lamps are powered? The resistor can be low wattage as long as the fet is turned off fast enough. If they they sample the lamp load current once it's running, that could be simulated by pulsing the same fet aka pwm but very narrow power efficient pulses. If they are detecting d.c, it's more difficult. If their startup lamp test is done over tens of milliseconds, a capacitor on the fet gate will handle that.Tungsten lamps may be say 50 Watts, but the equivalent resistance at this wattage is for the lamp running. When the filament is cold, if they are testing for continuity, the filament resistance will be only tens of ohms. Whatever you do there will have to be one dongle per lamp. I'd try to avoid winding lots of 'L's. Changing coding is the smartest solution but I don't think there are options. Do Xenon kits give no problem because V.W use them? I suspect the Chinese kit builders will have reverse engineered from the OE parts? Some led bulb suppliers talk about using capacitors to fool the bulb monitoring, but until more is known as to how it's done I'm not sure.

A bulb that is dead (zero current draw) or pulling a current below the required amount will trigger the bulb out warning. At least That is what I am seeing in my experimenting.
That's what I saw on the puddle lights as I kept increasing the shunt resistance value. But I hadn't got a 'scope across it so I don't know if it was d.c fed or pwm. Thinking about it, the door puddle lights are on the cabin light system which is dimmed by pwm. If lamps are driven by pwm and you know the frequency, you can calculate capacitor values that will take the a.c current without dissipating power like a resistor.
 

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The idea that the lights use a PWM signal has a lot of merit. When I first installed my Xenons I wired them in with a separate wiring harness to prevent any damage from the in rush currents and feeds the ballasts pure dc from the battery. This harness has a relay. The first time I turned on the headlights that relay sang like a bunch of mad bees. Some capacitors were suggested. I tried them and the relay worked properly. I still have a spare. I will need to put the proper connectors on to connect them to my LED headlights. As is they are plug and play for the Xenon kit. When I get a little time and cooler weather I will hook them up to my LEDs to see if they work to stop the blinking. I can't answer the question about VW lighting setup between the Halogens my Eos has and the Xenons VW uses. My guess is the controllers may be different. I haven't seen the capacitors for the LEDs, but have seen a couple different adaptors. I thought those were for the CanBus.
 

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OE Xenons could be using a different system for bulb failure or similar done in a different way. When a halogen bulb lights there is an initial high inrush surge current that doesn't last very long before the filament burns at the normal lamp running current. If the lamp is turned on and off within a short space of time e.g main-low beam-main, the filament doesn't have time to go cold and the inrush surge current will be lower. The lamp test/failure monitoring would have to allow for this as well as low battery reducing both the inrush and running current

OE Xenons have a totally different start up behaviour: Before the arc strikes there's a huge current surge for mSecs for the high voltage igniter, then the arc fires and the ballast circuit regulates (by PWM) the running current of the lamp. The load seen by the battery is a combination of very high short period current surge and the pulsed current for the ballast. When the battery voltage falls e.g low battery or cranking, the current into the ballast increases - which is the opposite behaviour to a tungsten bulb.

I can only look into the behaviour of tungsten bulb monitoring because that's what I have. If I'm right about OE Xenon I would expect different versions of the headlamp controllers for tungsten and Xenon, or the same modules with different software inside, or an adaptation option to set different bulb monitoring behaviour. Somebody with a parts list or who has fitted OE xenon could confirm? The addition of capacitors and resistors are the hacks I've seen used to sell the Xenon kits, but I wouldn't rely on them working for all car brands and hidden from you could still be the nuisance of having DTC fault codes triggering all the time whilst not putting on the bulb fail.
 
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