Common furnace problem
This winter I've had two service calls on newer 90% efficient furnaces. They have pressure switches that are designed to keep the furnace safe. They have condensation lines that can be plugged and cause the switch to shut down the furnace. I started one furnace on a project house in 0% weather so I could so some work. The furnace started working, created condensation which then froze because the house was so cold which caused the switch to shut the furnace down. The other service call was because the condensation line got dirty and plugged which caused the switch to shut the furnace down. So far, I haven't tried to fix them myself, but I may try now that I know it is a common problem.