True CANBUS error free LED red brake lights.

[GTI JOE]

Hi Guys,

Just wondering if anyone out there has installed LED red brake lights that ARE TRULY ERROR FREE?

Just purchased some off Ebay (not exactly cheap) and they throw up check light error

Link is Upgrade Car Back LED Tail Light Bulbs 382 P21W RED SMD Canbus No Error Free 12V | eBay

Willing to even try the CREE type if they are any good

[wai]

By the way, if you have a coloured tail light lens, you might not get what you expect if you use a coloured LED.

Basically, the reason you see a red light is because the lens absorbs all the colours except red and passes that through. If you use a red light and the characteristics of the red light does not match that of the tail light lens, you will find that the lens might absorb some of the light produced and pass only that the lens allows through. This is basically why the original bulbs are not coloured.

I went through this exercise on my last vehicle (Hiace ABV) where I fitted LED bulb replacements. The set I got had a coloured dome, and the light coming through the lens was very dull. Dremel tool and a little time saw me cut off the coloured dome and the light seen through the lens improved dramatically.

By all means, you can get the coloured LEDs, see if you can check them out before you buy. The white ones might be better.

[nomadx38]

Yep agreed with pervious post.

Also ALL LED bulbs will throw up an error becuase the use less power (and thus less resistance) than filament bulbs. To get around this you can put a load resistor in the circuit (but it is a lot of work!) OR you can just plug in your VAGCOM and go to central electrics II and disable diagnostics on the circuit (Brake/indicator/parking light circuit)

[GTI JOE]

I do understand all of what was said above, just trying something on my car. So I guess there is no true error free led lights out there.

Thanks nomad, didn't realize that the check light feature can be disabled, might try this avenue or just live with the instrument light on..no biggy.

[nomadx38]

No probs, at the next get together I will probs bring my VCDS cable so people can fix their cars up, so if one is organised I can do it then.

[GTI JOE]

No probs, at the next get together I will probs bring my VCDS cable so people can fix their cars up, so if one is organised I can do it then.

Much appreciated mate

[ecks]

(and thus less resistance)

Nah ah - more resistance

[nomadx38]

No less resistance in this situation. the electrical system is looking for a load of .41amps (5 watts divide by 12 volts = .41Amp for a w5w Parker). When the system sees it it using less power than this (+ or - 10% or so) it displays the circuit as been open. A 1watt led is only pulling .08 amps as is counted as blown.

A 100w incandescent bulb is brighter becuase of the resistance that is created by going through the very thin wire (a bottle neck) and the resistance is displayed as visual light, a by product of heat.

A 25w incandescent bulb is duller because of the thicker wire allows more power through and thus less resistance, and equals less heat/light.

The point of a load resistor is to put extra load onto the circuit to make the computer think there is a bulb.

Actually I'm happy to be corrected, it has been a while since I did my studies with Ohms Law and resistance so I'm a little rusty. I always pictured it as a freeway. Traffic will flow faster (and thus less resistance) going from 3 lanes to 2 lanes than going from 3 lanes to 1 lane.

[GTI JOE]

Yep^^^ the LED is showing less resistance to the electrical management unit, that's why the check light is coming on, thinks something is blown.

I would also imagine that the load resistor would be dissipating a fair bit of heat, so it would require some form of heatsinking.

[ecks]

I'm struggling to interpret your reply...

Load resistors go in parallel with the globe, therefore reducing the total resistance. More resistance = less current to flow. An open circuit is infinite resistance (well, in theory, until you reach a high enough voltage to arc, then you can measure the resistance of the air gap...).

Not being a smart-ass, just don't like seeing mis-information

[ecks]

Yep^^^ the LED is showing less resistance to the electrical management unit, that's why the check light is coming on, thinks something is blown.

I would also imagine that the load resistor would be dissipating a fair bit of heat, so it would require some form of heatsinking.

NO NO NO, it's showing MORE resistance, therefore LESS current is flowing!

[nomadx38]

I think you may be misinformed, though it sounds like you know a bit about electronics. Feel free to look this up on Wikipedia yourself but here is two parts of interest from "Electrical resistance and conductance":

"Geometry is important because it is more difficult to push water through a long, narrow pipe than a wide, short pipe. In the same way, a long, thin copper wire has higher resistance (lower conductance) than a short, thick copper wire."

"Objects such as wires that are designed to have low resistance so that they transfer current with the least loss of electrical energy are called conductors. Objects that are designed to have a specific resistance so that they can dissipate electrical energy or otherwise modify how a circuit behaves are called resistors."

A LOAD resistor would be placed in Series (not parallel as this would make two circuits side by side, thus the word "parallel") in the circuit to dissipate electrical energy (as heat) as to put more load on a circuit...

[wai]

Yep^^^ the LED is showing less resistance to the electrical management unit, that's why the check light is coming on, thinks something is blown.

I would also imagine that the load resistor would be dissipating a fair bit of heat, so it would require some form of heatsinking.

And that is the pity of the system. Instead of utilising the lower power draw of LED systems and being able to alter the triggering current of the alert, the "kludge" fix is to introduce a load resistor so that the system still believes that there is a normal light bulb there, and this sees no benefit in lower power consumption.

Many years ago I used relays to trigger a brake light fail on my Mini (back in 197. I used the current flow in the earth tail of the brake light, and this held relay contacts open. If the bulb failed, the current in the earth tail would be lost and the relay would close, triggering a light on the dashboard (or what passed for one on the Mini). With LEDs and modern electronics, the same thing could be done more simply.

[ecks]

I think you may be misinformed, though it sounds like you know a bit about electronics. Feel free to look this up on Wikipedia yourself but here is two parts of interest from "Electrical resistance and conductance":

"Geometry is important because it is more difficult to push water through a long, narrow pipe than a wide, short pipe. In the same way, a long, thin copper wire has higher resistance (lower conductance) than a short, thick copper wire."

"Objects such as wires that are designed to have low resistance so that they transfer current with the least loss of electrical energy are called conductors. Objects that are designed to have a specific resistance so that they can dissipate electrical energy or otherwise modify how a circuit behaves are called resistors."

A LOAD resistor would be placed in Series (not parallel as this would make two circuits side by side, thus the word "parallel") in the circuit to dissipate electrical energy (as heat) as to put more load on a circuit...

And if you place a conductor (Copper wire, zero ohms) across the terminals of a battery, very briefly (until a part of the wire becomes vapour) you will have a high wattage (low resistance) power drain (and probably an elementary light globe haha).

In the case of the 'load resistors" that are sold to correct globe errors, these are wired in parallel (one side to positive, one side to negative) to the light globe, and you should know that resistors in parallel decrease resistance, resistors in series increase resistance.

There will also be resistors in series with the "LED globe" on a PCB somewhere, but these are of no concern in the case, as the LED's are usually optimal on around 3 - 5volts.

Less resistance = Higher load. They're inversely proportional. Think about it some more.

[ecks]

No less resistance in this situation. the electrical system is looking for a load of .41amps (5 watts divide by 12 volts = .41Amp for a w5w Parker). When the system sees it it using less power than this (+ or - 10% or so) it displays the circuit as been open. A 1watt led is only pulling .08 amps as is counted as blown.

You aren't mixing up Watts (power) and Ohms (load), are you?