Alternator belt problems

Hi all. New to this forum. And really struggling to keep my 2018 proace 9 seater on the road. Along with lots of other issues. This one is wrecking my head. 

Belt changed as it snapped last year. The one onto alternator. But it's noising again. When I got a mechanic to look at it. He taught it may be the pulley either on the alternator or the air con pump. 

But to me it looked so like it was the crankshaft pulley that was or is not running smoothly. 

Anyone with similar problems that might give me some help before big money is spent on this thing. 

Thank all for reading

Hi Paul,take a look at all the pulleys in the belt area. Look for any signs of wear, damage, or misalignment. You can also try wiggling the pulleys by hand to see if they have any excessive play

It's possible that the crankshaft pulley is not running smoothly, as you suspect. A worn or damaged crankshaft pulley can cause the belt to vibrate and make noise.

The mechanic mentioned the alternator pulley as a possibility. A bad alternator pulley can also cause belt noise and vibration.

The air conditioning pump pulley could also be the culprit. A failing air con pump pulley can cause similar symptoms.

The tensioner pulley is responsible for maintaining proper tension on the belt. The idler pulley helps to route the belt around the system. If either of these pulleys fails, it can cause the belt to slip and make noise so check these. Hope this helps.