Our 29 year-old Carrier furnace relies on a 3-wire pilot with an intermittent spark igniter. It sparks probably around 30 times before the gas valve opens and the furnace fires up. That's a lot of sparking, and surely not good in and of itself, but the real problem is, it just keeps on sparking continually throughout the cycle, up until exactly the moment when the blower stops.
I would estimate it sparks twice per second throughout the cycle duration, roughly twice as frequent as the sparking that happens prior to the blower coming on.
Please note this furnace does not have a flame sensing rod. This is the bimetal type. Any suggestions on troubleshooting are appreciated.