Gas furnace problem

[brentj]

I have a Lennox furnace model GS11Q4E100-5NLT that started giving me problems. It was working fine but then it started short cycling on the heat cycle. What I mean is that if you set the heat to 70 degrees and say it was 65 in the house it would come on and run for a couple of minutes and then cut off before reaching the set temp. Finally it stopped working all together. I do know that this unit has the intermittent pilot so I had some help checking it and when you work the thermostat to call for heat the pilot lights. So I thought that the flame sensor had gone out. I replaced the sensor last night and am still not getting heat. I do not know where to go next with this. If I havent supplied enough information then let me know what else you need and I will get that on here.

Thanks

[nomadpeo]

also, is your thermostat digital or mechanical.

[4ftBanger]

It sounds like the ignition controls and components are working. If it were a flame sensor the burners would only stay lit for a few seconds (typically around 7) Based on your description I would suspect either a thermostat problem, or more likely a defective temperature limit in the furnace.

[nomadpeo]

if it is the limit, it may be doing its job when it sees too much heat buildup. this can happen if all the vents are not open or if the evaporator or filter are restricted.

if you have a mechanical thermostat, the heat anticipator could be set wrong. it is probably an airflow issue.

[nomadpeo]

agree with dilkey. measure temp of air in and out and compare against temp rise rating on nameplate. if too high, air is moving too slowly through the heat exchanger due to restriction and opening a limit switch.