Audi A4 B8 2009 - How do you wire a 7 pin plug?

frankdunleavy

My brother-in-law asked me to wire a 7 pin plug on his 2009 Audi A4 Saloon.

I had a quick look taking off the tail-lights to see if I splice into the wiring. Indicators no problem but Audi use a 21W sinlge filament bulb to act as the tail and brake light by varying the voltage sent to the bulb, e.g. 12 volts when the brake lights are needed and a lesser voltage for tail lights. Audi use a similar system on an 2006 Audi A6 I had, just complicated for the sake of it as far as I can see.

I could run a wire up to the high level led brake light to pick up the brake lights but this looks tricky. I still have have figure out how to pick up a 12v taillight point.

Anyone have any suggestions? I saw wiring looms on the net but they are costing over £120!
Thanks
Frank

martinr5232

You cant wire an ordinary trailer socket into modern cars you will send the electrics crazy.

You will have to fit one suitable for can bus.

frankdunleavy

Thanks martinr5232, he has a powered relay box as part of the 7 pin plug kit, do you think that I could still tap into the wiring using it. The car doesn't have led indicators or led brake lights.
Cheers.

martinr5232

frankdunleavy wrote: »

Thanks martinr5232, he has a powered relay box as part of the 7 pin plug kit, do you think that I could still tap into the wiring using it. The car doesn't have led indicators or led brake lights.
Cheers.

Im not sure how you would go about wiring into this without causing yourself hassle maybe a 120 quid would be money well spent might be cheaper than replacing the module if it gets spiked.

frankdunleavy

Found out that the relay box will work by connecting to high level Brake light and either the number plate or tail light in the boot lid but I don't know which wire these are in the boot area. I will find it out eventually, I just keep searching.