s3 lightweight, breaklight problem

[lightweight-love]

Hi my lightweight has 2 standard brake lights and 2 higher up, the N/S bottom and O/S top aren't working.
Someone said this is a classic sign of a bad earth knocking out horizontally opposite lights, so where are the earths?
just asking on here to save me crawling all over the place taking off panels etc looking for them!
Cheers for advice
Duncan

[TBM]

From your photo, it looks like you've got standard lights rather than military screw on ones. These lights usually have two points for earth - one is the light itself - it has a metal 'tag' that one of the fixing screws goes through. If your bodywork is well earthed, then this is sufficient. They also have a black lead which can also be earthed to the body work. Standard lights are usually earthed behind the panels in the corners.

I'd start by taking the lenses off and checking the fittings. They do tend to fill with water.