How do you change fan belt on a Vauxhall astra?

To change the fan belt on a Vauxhall Astra, first ensure the engine is off and cool. Loosen the tensioner pulley by using a wrench to relieve tension on the belt, then remove the old belt. Route the new belt according to the diagram usually found on a sticker under the hood, ensuring it's properly seated on all pulleys. Finally, re-tension the belt by adjusting the tensioner and check that it runs smoothly before closing the hood.