How do you replace alternator belt on citroen c4 hdi with air con?

To replace the alternator belt on a Citroën C4 HDi with air conditioning, first, ensure the engine is off and cool. Loosen the tensioner pulley by using a wrench to rotate it, which will allow you to remove the old belt. Route the new belt according to the engine's belt diagram—often found in the engine bay or in the owner's manual—making sure it sits properly on all pulleys. Finally, re-tighten the tensioner and check the belt alignment before starting the engine.