How do you change a fan belt on a vectra B 20i 140?

To change the fan belt on a Vectra B 20i 140, first, ensure the engine is off and cool. Locate the tensioner pulley and use a wrench to relieve tension on the belt, allowing you to slide the belt off the pulleys. Install the new belt according to the routing diagram usually found on a label in the engine bay, then reapply tension to the tensioner pulley and double-check that the belt is properly aligned. Finally, start the engine briefly to ensure the new belt operates smoothly.