Dodgy help?

[Webboo]

When I indicate left, the rear one is very feint, also when I lock the car with central locking the left brake light comes on and rear left indicator is very feint, I've been told this could be a dodgy earth but where would the problem actually be?
Its on a mk2 ph1 by the way!
any quick help would be appreciated as I'm sitting in the back with the door card off looking for it now, with no luck:dapprove:

 

[MicKPM]

The problem could be with any number of the earths on the vehicle... so you need to check them.

Start with the lighting loom earth seeing as that is where the problem is manifesting itself. They can be found near the lights themselves