hi my problem is my car stands on tick over fine at under 1000rpm but when you are driving and its got warm when i slow down coming to a junction for instance the revs drop and the battery light comes on then revs go back up and light goes off its seems as though its going to stall but doesnt then once i have stopped it ticks over fine its only when im slowing down the revs fall can anyone help its a 1.8 petrol

thanks rob