Why does the fan belt on my car squeal on start up?

My 2001 Toyota Yaris 1.3 SR has a noisy fan belt on startup but once driven for a couple of minutes it stops. My mechanic said it is because it has not been driven much lately?

Asked on 11 August 2019 by Dilys Warner

Answered by Honest John
He's right. The heavy work imposed on the alternator to put charge back into the battery is causing it to slip. A fresh belt will fix that.
Similar questions
When my neighbour fires up his Porsche, it sounds as though an explosion has taken place. Is this noise standard or can it be 'tweaked' in some way? Is there a legal limit to the noise that cars can produce?
I have replaced the squealing alternator belt with a new one but it is no better. What's wrong?
When warm and idling, I can hear a whining noise from the engine of my 2014 petrol Ford Kuga 1.6 2WD. This happens with or without clutch depressed. It disappears at other revs.

 

Value my car