I have a Loud Clicking coming from the drivers side from under the bonnet it sounds like a relay it does it if the turn the heating to 1 or turn it off also if I am driving with the heating on I keep hearing the clicking noise

What could be the problem ... Thx

 

Could be something simple like a (leaf/twig) gone in the fan inlet and either hitting the fan as it spins either whilst running or with the natraul air flow entering it turning the fan whilst it free wheels so to speak as your driving along.