CANbus LEDs - how do they work?

[JayTeeA38P]

What I'm mainly wondering is, as these lights are "fooling" the car into thinking there is a higher wattage bulb present than there actually is (if my understanding is correct), will the car still know when the LED has blown/broken, and give an appropriate warning message on the instrument cluster as normal?

 

[SootySport]

That’s a good question and I don’t know for sure. I would assume if the resistor breaks or the entire bulb came loose the bulb warning would come on but if the led failed only then no warning would show.

 

[downtothebone]

So I had a bulb partially stop working - I think half the leds went out and the rest were fine. There was no bulb error. I only noticed it when the reflection in the car in front seemed less bright on one side (drl bulb). Did have another completely fail but can’t remember how I noticed it.

 

[JayTeeA38P]

Thanks guys. That seems to confirm my suspicion.

 

[downtothebone]

Problem with led bulbs in standard circuits is the led units don’t use much electricity but the resistors have to convert the full current into heat so the entire unit gets very toasty unless you have resistors inline attached to metal to dissipate the heat.

 

[JayTeeA38P]

I see. Luckily all of my LEDs are for lights that don't stay on a long time, like internal ones, reversing lights. It's just the number plate lights that could get warm.

 

[JayTeeA38P]

I guess also you don't see any power efficiency savings from LEDs vs halogen, since it's still pulling the same current - just converting some of it into heat?

 

[downtothebone]

Well it should use less but not as much as a dedicated circuit since it’s down to current draw - the resistor is preventing the full voltage from hitting the led, the led itself will draw less because it needs less to light. The ironic thing though is you find lots of aftermarket led bulbs are packed with leds as this helps offset the amount of voltage you have to resist and there the amount of heat your need to dissipate. The downside is they are then too bright.