LED Brake Bulb Wont Light Up

need put 100w 8ohm resistor across brake live wire and earth

 

That resistor is perfect and yes need one each side car so 2 resistors. There is one more requirement and that’s the correct LED unit, I’d have to go measure the impedance of mine as either the CAN bus unit is the one or one without CAN sadly only one works and can’t remember which

 

Do these not get really hot?

 

The resistors tend to get very hot, be careful

 

50W for indicator and 100W for brake light, mounted to metal body help dissipate heat, works really well but if was doing again would use 2x 100W
The 100W doesn’t get as hot but still best not keep foot resting on brake pedal for extended period

 

To turn on the light bulb I believe no resistor is needed. The resistor serves only so that no error appears on the board. The problem with no name Chinese bulbs is the small difference in light intensity when activating the brake . if we are talking about a light bulb P21/5W LED.
I tried a bunch of no name bulbs. I ended up buying this

https://www.philips.co.uk/c-p/11499XURX2/x-tremeultinon-led-gen2-car-signalling-bulb.

They are much better than ordinary light bulbs. The lights look better because of the red color, which is more intense than on a regular light bulb. Yes, and most importantly when braking, you can clearly see twice as much light

 

on the mk3 megane when side light is activated there's for some reason voltage appearing on brake light circuit as well, not enough to illuminate an incandescent bulb but certainly enough to illuminate the brake side of the LED unit hence the resistor to soak up this stray voltage

 

also the impedance of the dual circuit LED you choose to replace reg 21/5 bulb seems to matter as well, some are LO imp others are HI imp

 

afraid its bit of a lottery with LED bulbs some seem to work better than others

 

How exactly did you accomplish adding these extra LED lights to your taillight? You may have made wiring errors, causing the dash computer to be unable to allocate the moments when the extra lights should come on.

 

2 years too late @ursalacim

 

Try removing the entire addition, and do it all over again with good quality and correct instructions. If you keep making mistakes, you better ask some proper questions to a professional electrician and so on. I like my lights to be very bright and noticeable, especially on the taillights. I bought LED strips at vont.com and installed them from a youtube video guide. In our state, fog and rain are common, so strong taillights are essential to the car.