i've been having a problem with my battery light coming on for some time now. it usually comes on when i start up after a stop or when idling for an extended period. will only go off if a then drive for an extended period.

have had it checked twice at the dealers who can't find anything wrong. i suspect the alternator's going but its still under warranty so i want them to replace it...if i take it in again, what kind of test should i get them to perform and what kind of results should i be looking to see?

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asiax | x5 xdrive35i | 2011 | alpine white on black on bamboo | 19" 334s | bmw performance aerokit & grille | aluminium running boards | stainless steel pedals |