Is that a hatchback? It definately sounds like a grounding issue on the right like the tailight is grounding thru the brake light filament.

Paul

 

The shared ground (under the boot carpet on the rear edge of the boot) was crusty and corroded. But I restripped it and it’s good as new. No change.

Do the tail and stop lights have a different ground? I checked the one on the rear wiper motor. That looks good as new.

Could it be the lamp holder / connector? Or the wiring running to the boot lid?

Cheers.

 

What body style?

Do the tail and stop lights have a different ground? I checked the one on the rear wiper motor. That looks good as new.

Could it be the lamp holder / connector?

I only have access to US Focus info. If your UK Focus is the same as US Focus (for 2004) then each lamp socket should have three wires: one for tail light, one for stop light, and one for a common ground for both filaments with an internal connection in the socket. However there are separate grounds for each socket (each side).

Paul

 

Hatchback yes.

Not sure about the no. of wires, but 3 sounds about right.

I will change the bulb holders over and see if the problem switches sides tomo.

 

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Thanks for all the help.

Changed out the lamp holder and it fixed the problem immediately. Did the same with rear fog which was also knacked. Fixed that too.

Also had a side and a headlight out! All bulbs (except left no. plate light) replaced!

 

I have the same issue mine is a 53 plate, 2004

The connection has been spliced from previous owner or something, see photos attached