Alternator light issue?

I bought a 300tdi Discovery for very little money due to being stood for a while.

I'm having an issue with the battery light, when I switch on the ignition the battery light is bright, same as the other warning lights, when i start it up the battery light goes dim so I figured the alternator was goosed. However it's still charging, even with the headlights on and everything switched on the headlights don't dim at all!

Is it an earth issue or is the Alt buggered?

this indicates there is an issue with the small diode trio or the regulator drawing some energy from the battery to charge the field coil. just means it uses more battery power than normal