Facelift LED Brake Lights

[Zulu4]

Hi all,

I have read about people updating pre-facelift brake lights to LED with some involved fettling, but I couldn't find much info about post facelift.

Bought a pair of CANBUS P21W LED lights, put them into the brake light sockets and ... nothing. Rotated them to check for polarity, same. Swapped side to side, same. Checked by wiring LEDs directly to a battery, they work OK.

I thought maybe the standard brake light bulbs were being lit by 6v, but I've just measured the voltage at the plug and it is 12v at the black and green wire.

I'm confused. Anyone know why the LEDs won't light ? And has anyone bought a set that do work ?
Thanks.

 

[Scooba_Steve]

I'm confused. Anyone know why the LEDs won't light ? And has anyone bought a set that do work ?

Polarity?
I have OSRAM LEDriving Premium for brake and indicator, they work fine. Though you do need to code out the bulb checks to stop the dash warning and test flickering.

Make sure you get red for the red lens rather than white. Also avoid CANBUS compatible, they're not smart they just have a load resistor to mimic a standard bulb.

 

[Zulu4]

Great. Thanks for the info Steve.

 

[LittleZ4]

Check the pins are in the same position on the bulbs, the led bulb may have symmetrical pins and the original my have offset pins. If they don't line up then it'll frustrate the sh!t out of you trying to get it to work!!

 

[Zulu4]

Thanks guys, the pins are correct and I've checked polarity. I think the bulbs I bought just aren't compatible with the Z4 ZX81 ( ) CANBUS. Perhaps they're not drawing enough current ?

 

[G600]

. Rotated them to check for polarity, same.

Rotating the bulb won't change the polarity as the metal housing around the outside is one of the connections, try swapping the wires going into the bulb holder

 

[Zulu4]

. Rotated them to check for polarity, same.

:

Rotating the bulb won't change the polarity as the metal housing around the outside is one of the connections, try swapping the wires going into the bulb holder

Ah...of course. Thanks
I shall now go and sit in the corner with a dunce's hat on.

 

[Scooba_Steve]

Ah...of course. Thanks

You may not be able to switch the polarity that easily, from what I remember of the tail lights, there are solid metal contacts and the holder is keyed to one position only.

I suppose you could disconnect the pins in the wiring plug and swap +ve/-ve for the brake only to test. But I really think that's overkill as it's not a workable solution.

 

[DorsetWurzel]

DO not swap the wires round, if you are adapting the vehicle for things to fit, it isn’t the right part!

Try a different set of LED’s, if the ones you have bought are cheap and nastles there’s your problem.

I’ve fitted LED brake light bulbs to mine with no problems, just had to code out the bulb failure light. I will try and get a pic at some point today.

 

[G600]

What's the reason not to swap the wires over then?

 

[DorsetWurzel]

What's the reason not to swap the wires over then?

One is the ground and the other is 12+VE supply and I expect it’s a common ground, so you would be chucking 12v straight to ground.

The cars wired right, the bulbs are the issue.

 

[DorsetWurzel]

Here is a couple of the LED brake light bulbs in my Facelift E85.

 

[Scooba_Steve]

What's the reason not to swap the wires over then?

Exactly as Dorset says, have a look, the contacts are solid in the light housing so there are no wires into the bulb holder. It’s not a workable permanent solution, so while it would work to test, it’s a bit moot.

IMHO, get some proper ones, code out the checks, job done.

 

[Zulu4]

Thanks for all the good advice chaps. 8)

 

[G600]

What's the reason not to swap the wires over then?

One is the ground and the other is 12+VE supply and I expect it’s a common ground, so you would be chucking 12v straight to ground.

The cars wired right, the bulbs are the issue.

Aaah ok, pre facelift it's all individual bulb holders/grounds so it's not an issue on them, I assumed the facelift would be the same.