As both work at some point , this would suggest the led is okay . A normal failure of an led , is usually the led itself .
I would suggest this is a wiring problem , and the weak right would lead me to believe it's an common earth , meaning a main earthing point . I'm guessing it's Ducato based , and this further reinforces this as i'm afraid earthing issues are quite common on dukes .
My own Hymer suffered a total fog light light failure , which i eventually traced to an earth from the relay , which is behind the dash ! .
