On my 4/4 there was a squeal at around 5 years old. I changed the alternator belt and the squeal vanished. I now change the belt at 4 years. They cost so little and are so easy to change, it’s not worth waiting for a failure.
Paul Costock, UK Plus Four 75th - Furka Rouge - Pip Disco 5 Teddy - 17h1 Irish Draught cross