After sitting in my Renault Espace with the air con on (for 20 mins) a warning light then came on saying "battery charge fault". I had the car checked and the battery is fine. However, while looking under the bonnet and turning the air con on, the fan belt seemed to slow and stop for a few seconds this continued until the air con was turned back off. Any ideas on what has happened? I wonder if the air con pully is seizing up.