Crazy S3 Electrics

[PeterC]

Help and advice needed please. Having minor problem with electrics on car. Recently noticed (dark nights) that when I press the brake pedal, the side lights and dash lights come on?

Everything else seems to be OK.

Unlikely to be water related problem as car is only used on dry days and garaged.

Thoughts - the only commom denominator would seem to be the earthing to the chassis located behind the n/s rear wheel. But I have thoroughly cleaned this connection and problem persists.

[PeterC]

Thanks for all the info. It will be Sunday before I can try any of the ideas.

When checking all earthing points, how many are there and where are they?

[PeterC]

Thanks to everyone that replied, but I think I've found the problem

The stop/tail light bulb in the o/s rear light was faulty and both filaments were illuminating when I tested the bulb by connection a 12v test battery to either contact + earth.

I changed the bulb and the problem has disappeared (for good I hope).