Rear lights electrical fault - any ideas?

[flappy_paddles]

My 2000 plate 1.7 Zetec has deleveloped a problem with the rear lights. Whenever I turn on my lights (dipped and main beam) and then press the brake, the passenger side rear position light goes off and the near side rear position one brightens. When I take my foot off the brake, both rear position lights go back to normal. Rather than taking it to a garage, does anyone have any idea of which faulty wire I need to locate and/or replace?

 

[red]

Welcome to the site, good luck with resolving your issue.

 

[oilburner]

Make sure it's the correct bulb fitted and then make sure it's fitted the right way round.

 

[flappy_paddles]

It's only just started happening and I haven't replaced any bulbs recently.

 

[Frank]

Likely to be an earthing fault on the passenger side rear cluster or specific bulb holder.

Btw - 'the passenger side rear position light goes off and the near side rear position one brightens' - the passenger side is the nearside. You need to fix the side that the light is going off on and I figure you did mean the passenger side does that.

 

[zinc2000]

Agree with above, earth fault on nearside,but also worth taking bulbs out anyway and making sure they and the holders are clean and making good contact, little bit of moisture is sometimes all it takes to make the lights do their own thing.