This is an indication of failure of your alternator,

if the panel light is on and off when the enging is running. The panel light is on when your alternator is malfunctioning. The panel light is off when your alternator is functioning. On and off means your alternator is in the margin of good and bad condition. The panel light in fact is just a volt meter, it let you know the output votage/condition of your alternator. I'm pretty sure, you should replace your alternator. It is relative easy job if there is enough space around the alternator in your car. It might be less than $150 (you have to return the old alternator to where you buy the new one). I have replaced several alternators including a very old Camry's. The failure of an alternator in old cars always shows the panel light on.