I have a Heil furnace 90 plus mfg 1989, Heat cycle is satisfied and thermostat is not calling for heat. Induced draft motor starts, spark igniter starts, blower starts and runs like this for 3-4 minutes then stops. This repeats every 3-4 minutes until thermostat calls for heat then it works normally for the cycle. After cycle is complete the above repeats. Any suggestions are appreciated.