I have searched many forums for the answer to this question, I have replaced the rear twin filament bulbs with brand new ones, when the brake pedal is depressed the dash lights radio light and front side light bulbs illuminate, I have tested the 2 contacts inside the bulb holders and even though the light switch in the car is off both contacts are live, thus meaning the both filaments are lit up together,to eliminate it for now I have disconnected the central brake light, also with the lights on the brake lights seem brighter probably because they are both live instead of being on 2 circuits ! I have a 2004 focus tdci saloon,

Did this happen before you changed the bulbs ?

Yes I changed the fuse to the number plate lights and all was well until I noticed the fault at dusk one evening, decided to replace both bulbs with new ones but problem still exists and its mot day friday!!

There's a wiring issue / short circuit / earth fault somewhere on that circuit

I cleaned the earth wire in the boot and the one from the battery to body, also forgot to mention one of the number plate bulbs was what looked like "chromed" inside replaced that and was ok for 10 mins, is the number plate bulb circuit on the same as brake light and side lights?

The numberplate lights will illuminate with the side / headlights & may or may not share the same fuse & the brake lights should be on their own circuit with their own fuse

The shiny chrome effect in a bulb generally indicates that it has blown or is going to soon

Many thanks mark you have given me food for thought ! I will check and clean the contacts on the number plate lights and replace the bulbs ! I will post the results

No worries

Think I may have solved the problem, cleaned and sprayed the number plate light contacts and disconnected the boot lock loom sprayed inside the boot lock plug and reconnected, touch wood all seems to be as it should!!

nice easy fix!