I have a ducane furnace its about 2 yrs old when it is really cold out the furnace is unable to maintain temperature it will shut off and will not restart without going to the thermostat and turning it off and on again. This usually happens in the middle of the night when it is the coldest and only on really cold days. I have waited to see if it would turn on again but it doesn't do it on its own. The filter is clean and all of the vents are fully opened and working. We had this problem last year and called someone to service it they fixed it but now it is doing the same thing can anyone offer some advice?