battery light k12

[davidtl1000]

Hi I have reciently bought a micra k12 on a 2003 reg car drives fine but once warmed up the battery light flashes on during acceleration. checked alternator belt its nice and tight put an ammeter between alternator and feed to alternator and the amps/ voltage doesn't drop/alter any when the light comes on. Anyone had this problem before ( no fault codes stored)thanks David