How do you change a fan belt on a 2000 1.8 vectra?

Answer 1

There will be a tensioner pulley on the belt - loosen this first, then remove the old belt, taking careful note of where it goes. Take pictures if possible. Then put the new belt on and tighten up the tensioner until the belt is taut. Next, turn on as many high electrical load items as possible - headlights, rear windscreen demister, heater etc and start the engine. This loads the alternator, meaning the belt is under maximum tension. If the belt squeals upon starting it needs tightening. Obviously, if you can see it flapping about or vibrating a lot it needs tightened as well.

Note: the tensioner will be a pulley wheel which does not drive anything and it will have some sort of device, normally a bolt or a lever attached to a bolt, to move the wheel so that it stretches the belt when the bolt is tightened.