We have a Carrier Weather Maker Infinity 90%+ high efficiency, two stage, NG, forced air furnace that was installed in the summer of 2000. It works great in the summer with our Puron central air unit, however every winter we have the same problem. It turns off intermittently and won't go back on unless we push on the front door of the furnace, click the auto fan on the thermostat from off to on and back quickly (doesn't always work), or turn off the thermostat and then turn it back on (doesn't always work either). Pushing on the front door always works. There are no LED codes showing, the furnace goes on and off properly with the power switch, and the blower motor has been replaced. The thermostat has been replaced once by us and once by a service tech who put in a White Rodgers programmable thermostat (model 1F80-261). Same problem after a little while. The furnace manufacturer says it's a thermostat problem and the thermostat folks say it's a furnace problem. Neither of them has been any real help. Any ideas? I have to come home a few times a day and get up at least two or three times each night to check on it. Getting pretty cold here in the north land... Thanks in advance!

Next time it quits, pull the thermostat of the wall and jumper the red and white wires. If it starts up, it is the thermostat. If not, I would fine tooth comb any wires near the door. You can have a broken conductor held together by the insulation. Look for an overly flexible place in the insulation.

If it works when you push in on the door,check the dooor switch

Are there any wires near the door? Maybe a poor connection on the PC board you are correcting. I'm surprised there is no codes.

When you say there are no LRD codes showing do you mean it is not flashing a code or do you mean that the light is not burning at all. One suggestion is to make sure that you bottom door is one correctly and the door is latched into place. Pushing on the door is doing something to make it run and I am suspecting that what it is doing is engaging the door switch. I hope it is something that simple but the trouble that you have had in the past it hardly sounds like it. Good luck.

I have the same problem on my Carrier furnace whichis an 80% efficiency model installed 18 years ago. It is definitely the door switch in my case.