Hi everyone, I stumbled across this forum while shivering a week ago at my computer learning. I'm glad to say that the advice put forward on this site allowed me to pick up a heat ignition switch, instal it, and enjoy a warm nights sleep. I still have a reoccuring issue with the furnace. Simply put, I call for heat and it doesn't always respnd. Seems the thermostat has a mind of its own. I'm wondering if the heat sensor needs to be cleaned (I should just do it anyway). I'm fearing the circuit board may be in need of replacing. Also, sometimes the furnace sounds like it's about to fire yet cool air will blow for maybe 30 sec to 1 min then shut off. Any suggestions?

Try cleaning the flame sensor.

Start with the simple things as mentioned such as the flame sensor. From there you will need a multimeter to determine what is calling what to pin down the exact problem.