Have had ignition warning light come on 2 or 3 times recently, about 20 - 30 minutes after starting. It was going on & off for spells of 2 - 5 minutes, then yesterday after several on- off periods it stayed on for the remaining 20 minutes of the journey. Today, whilst cold, the light went out as usual on starting. As there is a delay between starting from cold, & the light coming on, I'm wondering if there's a diode pack problem? Advice please.