High level brake light to work with headlights on

[milescook]

Its actually a motorsport mod the brake light so please don't be offended OEM types

Problem is I've spliced into the wires near the aerial and hey presto the led brake light comes on when the brake lights do. But only when headlights are off. What's the simplest way of ensuring this light comes on when it's supposed to?
Cheers!

[Brianmoooore]

It'll help if you tell us what colour the wires are that you've connected into. I suspect you've connected to a brake light and a tail or number plate light wire.

[milescook]

Okay the wires I've spliced into at the moment are Violet (or purple)/red, and green/yellow.

The LED brake light is working when you touch the brake - I checked the wires using a multimeter. Sadly I didn't think about the different configurations of brake light depending on the whether the headlights were on.

Simply put, I need the light to work whenever I touch the brake no matter what. If there's two magic wires I just need to tap into to cover all scenarios - superb.

[Altrezia]

Should have been green with red stripe shouldn't it?

[milescook]

Instead of which wire...green and yellow?

[Speedtouch]

Green/yellow is fine - that's for the nearside rear stop light, but you need to just earth the other one (brown wires are earths on BMWs - either tap into one of those, or just use a separate wire direct to the car body):

http://www.e30zone.net/e30zonewiki/imag ... Lights.pdf

[milescook]

Ahh right cheers I'll give that a go. Wiring diagram looks handy - so BMW catered for a high level light too? Interesting...

[Speedtouch]

Yes, it appears so.

I guess that's to avoid any possible problems with the additional light affecting the "Brake Lights Fault Indicator" circuit, which is quite sensitive to load.

[Altrezia]

Sorry, I didn't read your post properly - yes, earth the other one as Speedtouch says. I presumed you had =)

[milescook]

Will be my next job, cheers all

[Brianmoooore]

E30 wiring design caters for a high level brake light, but that version uses a different bulb failure module on the left hand inner rear wing.
The correct way to wire your light is to take the + wire from your LED array to the green/red wire on the plug that goes into the bulb check module, and take the - wire to the earthing point at the LH end of the rear seat pan - the bolt with the brown wires going to it.

[milescook]

Earthed the other cable job jobbed! Cheers!

[Speedtouch]

Good to hear that!