Nissan Primera 2001 vibration sound at low speed

[mlawry]

Hi, I have a Nissan Primera P12 2001 wagon. It has developed a vibration sound (rattling noise) at low speed when starting off or with reversing. As soon as you speed up it disappears. Its coming from the right front of the car. My mechanic has looked at it a few times and now thinks (after talking with Nissan) this appears to be a problem caused by the alternator clutch not working properly anymore. This has then caused a problem with the tensioner arm not working correctly against the fan belt. So you get this rattling sound at low speed. Does this sound correct and has anyone else heard of this problem before? Thanks!!