What are the signs that I need the alternator in my Volkswagen Touran 2.0 TDI replaced?

Recently, the battery light on my Volkswagen Touran 2.0 TDI comes on above 3000 revs but as soon as I drop below it goes off again. There is also a whirring noise when starting the car. Turbo boost is fine so I'm thinking it's the alternator or the belt that's given out. Any suggestions? How hard is it to replace the alternator?
Check both the pulley and the belt in the first instance but if both are okay, then yes, replace the alternator. A good garage would replace in 1 hour.
Answered by Alan Ross on

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