it could be the earth cables its self if you have cleaned earthing points.. they get copper corrosion where only the plastic outer part of the wire is still there.. the inner part has just turned to a black non conductive powder
just replace the wire if so.
just make sure that you have really done a good job cleaning the earthing points.
there's one just in front of the battery, one just in front of the windscreen washer bottle and there's another behind the rear pass side tail light that only really earths the rear lights.
Thanks. I had trouble locating the earth point, don't know how! but now have cleaned it and lights are bright as they should be. Have to get some copper grease. Is there any thing that cleans off corrosion on the points, Like a liquid solution, beside emery cloth?
liquid solution.. hmm some kind of acid i guess a bit like soldering flux. i am not sure. i prefer the old fashioned way of doing it.
the copper grease just stops it from corroding again. after a few years it will look rough again but under the grease it will still be as clean as the day you sanded all the corrosion off it.
theres other tricks to make headlamps brighter such as thicker cabling.. and adding relays instead of having all the power go through the dash switch.
They're already relayed and the headlights don't directly draw through the switch, but it's the OEM wiring that deteriorates with age, hence rewiring with a new related circuit normally seems to make an improvement