Ford Focus Zetec 06 Brake Lights No Work When Headlights On

[TristanAvery]

So issue is that the all brake lights work when the headlights are off.
When the headlights are on, only the middle one (on the read window) works.

Had a look at the wires on the sockets of the builds, of both the front and rears. Couldn't see any corrosion.

Fuses are all fine. Bulbs aren't blown

Would check ground points, if I knew where abouts they were. If anyone can point me to diagrams/videos (hell even hand drawn would work)

Saw on a whirlpool forum someone had a similar issue and that their issue was the socket that holds the bulb. How would one check that?

[GasoLane]

Originally Posted by TristanAvery

Would check ground points, if I knew where abouts they were. If anyone can point me to diagrams/videos (hell even hand drawn would work)

Have you tried the Tech Resources?

[TristanAvery]

Originally Posted by GasoLane

Have you tried the Tech Resources?

Have had a look at the wiring diagrams. Can sorta read them and find grounds, just doesnt help with finding where I should look for said ground on the car.

Did check continuity with a multi-meter. Rear Tail light Sockets have continuity when head lights are off. As soon as the lights dial is turned to "park", the sockets lose continuity.

So that leads me to believe that the sockets have gone bad.

[marg99]

I would still be inclined to a bad earth which fails when asked to provide a higher current draw if possible undo the earthing mounts clean and retighten them. There is a major earth mount on the strut tower on LHS of engine bay in the early series focus.
Easiest check is to supply independent earth wire to the tail lights and see if your problem still occurs

[Smiddler]

Hi I know you say the bulbs are okay but it might be a good idea to replace them in case they are internally shorted I had a cruise control issue that turned out to b a faulty globe although they all worked