Doubling Your Brake Lights

Whilst changing a bulb "UK225" stumbled across a new Audi mystery,
both sidelight bulbs are dual filament 5w/21w bulbs but only one sidelight bulb turns bright on braking.

Thinking he had a fault, I checked my bulb holder and sure enough both holders are twin filament, the 2nd holder has the 5W power feed A. which leads to a bulb also has the 21w feed B. going right to the holder but is missing the bulb contact.

Why did they do this? To comply with UK regulations on fog lights.
Wiring this up may fail an MOT because the light is less than 10cm from the brake lamp, It also explains why Audi chose to illuminate the smaller outer lamps rather than the larger inner lamps.
 So be prepared to remove a cluster, Personally I don't think a tester will spot this but the risk is yours.

UK225 had already suggested wiring them up and I couldn't wait for him to try so another mod mission began to address making it work whilst maintaining convenience of changing bulbs!

I checked the brake light circuit and at 10A its more than enough to operate the additional 2 filaments.

Thoughts of drilling holes and soldering wires to bulbs were getting me down and what was needed was to actually fit the contact for the base of the bulb that should have been there in the first place.

BUT where to get this part, the original was a VALEO product so I went to a scrappers and found an Audi 80 and a Mk2 Golf, both of which had similar spring clips in their bulb holders.

You will need : -

A flame source and long nose pliers.