I've worked in the HVAC field, but I am stuck on this one. I'm sure it's simple. I cannot find my manual for my furnace. My furnace is only 4 years old. It has worked perfectly up till this point. The ignitor is working properly, we've replaced and reset the thermostat repeatedly, the fan is blowing in the heat exchanger. The problem is it is freezing in the house, but the furnace will not kick on until I manually turn the thermostat off then back on. Sometimes that doesn't work, I have to hit the reset switch on the furnace. Even when I do get it to come back on, it short-cycles and cold air blows out. I've had this problem on a standard pilot system before and replaced the thermocoupler, but I know that some of the electronic ignition units do not have thermocouples, they have "flame sensors" and the gas valve unit has to be replaced. It looks like I have a thermocoupler, but I know the flame sensors can look like a thermocoupler. Any help? I have a Janitrol/Goodman unit.