oh, dear............(oops)

can't think what exactly is happening but LED's have literally no resistance compared to a filament bulb so with no series resistors you will have mucho current flowing through your LED's compared to what was flowing when you had bulbs. i dont know whether those LED "bulbs" have series resistors built in or not?

danregs said:

can't think what exactly is happening but LED's have literally no resistance compared to a filament bulb so with no series resistors you will have mucho current flowing through your LED's compared to what was flowing when you had bulbs.

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That's not correct.

Yes, LEDs have very little resistance, but these bulbs have a whacking big resistance built into them - otherwise you'd get a nasty burning smell as soon as you applied 12 volts to them. These bulbs are designed as drop-in replacements for the standard conventional bulbs.

So these bulbs actually have a far greater resistance than the standard bulbs. How that can be causing the symptoms is a bit of a mystery.

We really need a wiring diagram for the car, don't we? Come on Haynes - do the Mk4 Ibiza!

You could try fitting load resistors across some (or all) of the bulbs. If you choose the resistors correctly, it'll cause the same current to flow as if you had conventional bulbs, but this is starting to sound like too much hassle.

Yep seen this before, just not quite as serious. On Mike_OBD's - changing the brake lights to LED's made his heat plug light flash (electrical fault) and his TCS wouldnt turn ON! Also the rear brake light stayed very dimly lit (which looked cool). God knows what else was buggered but needless to say, we got em all out! I know the side-lights are safe, but i wouldnt bother with anything else!

dmjw01 said:

That's not correct.

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uhhhh nope! what i wrote is correct! (not proud of it but i'm an electronic engineer )

if you read the rest of my post, i was asking about series resistors built into the LED "bulbs"... and you've just answered my question... there ARE series resistors built in

interesting thread though. i was considering making my own LED bulbs for my car but if there's gonna be load problems that cause all sorts of mayhem then i don't think i'll bother!

Sorry - I did read your post a bit too quickly! I don't think we're in disagreement.

I find it a bit scary that the engine management and TCS (and probably also the ABS) throw a wobbly as a result of a fault in one of the lighting circuits. Surely these should be designed to be as independent as possible? If it can't cope with an increased resistance, I wonder what will happen if several bulbs fail completely? It would be interesting to see what happens if you remove all the bulbs throughout the car, and see what stops working!

dmjw01 said:

Sorry - I did read your post a bit too quickly! I don't think we're in disagreement.

I find it a bit scary that the engine management and TCS (and probably also the ABS) throw a wobbly as a result of a fault in one of the lighting circuits. Surely these should be designed to be as independent as possible? If it can't cope with an increased resistance, I wonder what will happen if several bulbs fail completely? It would be interesting to see what happens if you remove all the bulbs throughout the car, and see what stops working!

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thats ok mate

and yes i agree with you... it is scary that these "bulbs" are effecting important systems like the ECU and TCS... and ABS is even more scary as your braking system is prob the most precious system in the car!!!!

are these LED bulbs e-marked?

the company should really be informed of these effects so that they can either warn customers or look into the problem and modify the bulbs. its in their interest, before someone decides to take them to court when their ABS doesnt work or something!!

danregs said:

are these LED bulbs e-marked?

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Admittedly, no they're not.

But of course that doesn't automatically mean there's something strange about them electrically. It just means that the manufacturer hasn't gone to the expense of doing the type-approval procedure.

My bet is that the market for retrofit car LEDs will grow as more and more brand-new cars have them - people are going to want them on their older cars too. Hopefully that means the potential revenue will make it worthwhile getting the e-mark, so in the future we might be able to buy e-marked LEDs. We can hope...

I've got an LED reversing light and fog light, and they give no problems that I've noticed. I might try sticking a meter across one of them and check that the resistance is sensible - although I assume it will be much higher than a filament bulb. But I haven't got one of the stop/tail LEDs to test.

This is all very disappointing. I was hoping to use LED stop/tails as well as indicators, at least on the back.

this is caused by electronic central electrics control unit to much drain/power from brake light switch

I'm not sure what you mean there. The LED bulbs should be draining a fraction of the power of the conventional bulbs - isn't that what you'd expect?

down to amps drained not voltage how many leds are there?

A stop/tail LED bulb typically has thirty or more individual LEDs in it. But the total current drain of all those LEDs combined is still a fraction of a single conventional bulb, as I understand it - that's meant to be one of the advantages of using LEDs.

When I get home I'll measure the resistance of an LED bulb and compare it with a conventional 382 bulb (haven't got any 380 stop/tail bulbs to play with). That'll tell us what the current draw will be at 12V.

I = V / R

tiny resistance of LED's = large current drain

this should only happen if the company have got their series resistance wrong in the LED "bulb". if they have added the correct series resistance then current drain SHOULDN'T, in theory, be a problem

oh and remember when measuring the resistance of a filament bulb that the resistance of it cold (off) is different to its resistance when it is on

would be interesting to get to the bottom of this...

Its A Safety Feature

The same thing happned to my car when i put new LED bulbs in the rear light clusters! Basically because the Voltage used is so much lower the ECU thinks the back lights arent working and as a result everytime you brake then accelerate a message is sent to the ECU to in essance cut the power to the engine to force you to pull over and not continue with the journey as its unsafe to do so! quite clever little thing but annoying if u have LED bulbs

the voltage won't change. it will always be 12V

the current drain will be monitored tho! and the Central Control Module tells the engine to cut the power to make you ull over. that would explain whats going on.

BUT, if the company got the resistance of their LED setup right then this shouldnt happen because the current drain would be the same as a standard filament bulb

danregs said:

BUT, if the company got the resistance of their LED setup right then this shouldnt happen because the current drain would be the same as a standard filament bulb

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I'm 99% certain these LED bulbs do not have built-in LOAD resistors. They have built-in SERIES resistors so that you can just plug them straight in without them disappearing in a puff of smoke as soon as you turn them on. But they are intended to be low-power bulbs.

If they had built-in LOAD resistors, then their resistance would be about the same as a filament bulb (though thanks for reminding me that a filament's resistance will be different when hot - greater resistance when hot, right?).

I'll stick a meter across one of these babies tonight. I'm expecting to see a very LARGE resistance, due to the large series resistor built into the bulb.

If this is a "safety" feature to deliberately cut the engine when it sees an unexpectedly small current going through the brake lights, I think that's a pretty questionable safety feature. A lack of brake LIGHTS isn't going to send the car out of control, but a sudden loss of engine power might (especially if it takes the driver by surprise).

But if that's the case, at least we might be able to fit load resistors across the brake light contacts of the bulb. This problem might still be something that can be solved.

dmjw01 said:

But of course that doesn't automatically mean there's something strange about them electrically. It just means that the manufacturer hasn't gone to the expense of doing the type-approval procedure.

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Not quite true, if they aren't ECE27 compliant and hence E marked, then they don't comply with the Road Traffic Act are are technically illegal.

I doubt anyone will notice.

Simon.

TheOtherSimon said:

Not quite true, if they aren't ECE27 compliant and hence E marked, then they don't comply with the Road Traffic Act are are technically illegal.

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I know it makes them technically illegal. My point was that the lack of E-mark doesn't automatically explain why they don't work properly.

I was also trying to say that just because they don't have the E-mark doesn't necessarily mean they couldn't get the E-mark if they wanted to. But I bet you it costs a lot of money to go through the necessary approval procedure, so for small volumes the manufacturer won't bother.

dmjw01 said:

(though thanks for reminding me that a filament's resistance will be different when hot - greater resistance when hot, right?)

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yep

oh and its the SERIES resistance that gives the LED bulb setup the correct LOAD resistance, so they are one in the same

the only other type of resistance (other than series) that you could introduce to the LED bulb setup would be a parallel resistance but this would not make any noticeable difference because the LED's have such a tiny resistance

Ultraleds publish the current draw of many of their LED bulbs.

For example, this 16 LED White 382 bulb draws 90ma (naff all, in other words!)