Hi 

I have a 05 octavia. tdi with 923000 km.

the headlights have gone dim. maybe an earth wire issue?. any help please?

Given the age/kilometres of the car and both lights are affected I'd say your diagnosis is correct.

 

Check all ground connections and rectify as necessary.

Anything else running poorly - could point to an alternator issue

If the alternator was faulty the battery wouldn't charge fully and starting would become an issue.

 

If the battery is faulty the lights would noticeably dim during gear changes as engine RPM/alternator output is momentarily reduced.

All fixed lads. Issue was bulbs i put in had not proper wattage. 

in picture bulb box on right is incorrect one.

 

Thanks anyway