I have a Bryant gas furnace 383KAV that is 7 years old. Currently the burners come on and then go off after a few seconds. After this happens 4x the furnace delays for 3hours. I thought the flame sensor might be dirty - but I cleaned it some and nothing came off. That didn't help. Filter is OK. I checked voltage at flame sensor. It is ~10.8 volts cold and when burners come on it jumps around sometimes reaching 18 volts but it is not steady. Occasionally the burners will stay on and it operates normally, but the problem is rather consistent today.

Do I need a new flame sensor?
Is this just a thermistor to ground? Or is it a thermoswitch?

Thanks for your help.