Assuming the belt and pulleys are in good shape, put a dab of clear silicone grease on both sides of the belt. Do this with the engine off. Squeak is gone.
Either the belt is worn out or the tensioner is defective.
oil it or shoot a squealer
Replace with Good Year Gatorback belt. Costs more but worth the money.
It could mean the beginning of the end for your belt or the idler pulley, have them both checked out.
A squeaky alternator is sometimes a sign that the fan belt or something associated with it is squeaking, not the alternator. (Possibly the belt or belt tensioner) So first I'd make sure it's actually the alternator squeaking before I proceeded. You could try some belt dressing on the belt and see if that helps or changes the squeak. If however it is the alternator, that's usually a sign the bearing's gone out and you will need to replace the alternator.
If the motor has oil ports you can put in a few drops of oil. If the motor has sealed bearings you will need to replace it.To fix a squeaky furnace, you need to add oil to the motor bearings. In some cases it could also be due to the fan, which would then need to be replaced.
A squeaky belt is usually caused by a bad belt, a missaligned pulley, or something leaking on the belt.
With engine off try putting a small dab of silicone grease on each side of the belt. It works for me.
First, you need to inspect the belt for cracks and defects. Also make sure that the belt is still flexible. If it does not have any problems, use tension bolt to tighten the belt.
how to fix belt for peugeot 207 diesel
It is in the factory. To get it, fix the conveyor belt.
change it