I have a 15 year old Heil gas furnace that just started blowing cold air. Called a service company to fix it (at a cost of $300) and they replaced the controller with a universal one. It seemed to have fixed the problem for a few hours then went back to doing the same thing. After no heat overbite I attempted to check it out my self and found the ignitor wire was not seated all the way on so with the furnace off I reconnected the ignitor wire. That too seemed to have fix the problem but not really. After a few more hours it stopped restarting again. Could I be looking at a faulty flame sensor/ignitor? If not what should I be looking for?

I have a payne gas furnace that is over 16 years old. Last night I noticed the thermostat was set to 68 degrees and it was 65 in the house. Honeywell digital thermostat showed " Heat on" but it was not. I removed the cover to the furnace which releases a switch and changed the filter which was last changed about 2 months ago and also cleaned away some dust. when I replaced the furnace cover the furnace immediately kicked on and brought the house temperature back up to it's set point and turned off. Woke up cold in the middle of the night and discovered that the furnace again did not kick on . Again, I removed the furnace cover and then replaced it, resetting the switch and the furnace again immediately kicked on. This morning same issue, the heat did not come on until i reset it again. Is there a problem with my termostat? Any suggestions on what I can do before calling for service? Thank you