Hi All,
Thgank you all for your thoughts and advice.
I have just run an earth wire direct from the battery and connected it to the black wire and it still doesn't work, so I have run a 12v supply direct from the battery and connected it to the white wire terminal in the plug and the light works. So it is the live 12v freed that is faulty.
From the battery at the end of my temporary feed I get 12.8V but on the 12v feed to the light I only get 12.15V so I am assuming I have a bad connection somewhere.
I would think that the most likely place is on the gearbox connection.
Can anybody tell me where to look for this gearbox switch. I have found a 2 wire plug on the front of the gearbox behind the air filter housing, is that it?