how do i fix my electrical fault on my golf mk2?

i have a golf mk2 that is playing up it seems i have an electrical fault but i cant find it, the engine starts ok and will drive but when ignition is on the battery light is on constantly it seems to get dimmer the more you rev it but is still visable, i have taken out the cd player incase there was a fault on its wiring i have a rusty indicator which i have also disconected i have looked under the bonnet to make sure all leads are connected and also checked for faulty fuses can u help? thanks