Long story but yes I discovered the issue. Themostat tripped which shut down the furnace in a heating cycle, which then threw an HVAC error of “Limit Switch Circuit Open”. Upon reset of the Thermostat, the furnace would come back on for about 30 seconds and then shut down again. This cycle kept repeatin g itself. When I replaced my furnace last the techs installed the electronic air filter that was in the old furnace, but I stopped using it because of the cost of replacement filters. I started using standard filters and unplugged the electronic air filter. The plug was wired into the fan wire obviously and every now and then brushed up against the metal of my water heater which would generate a bit of an electrical surge to the thermostat, tripping it and starting the cycle. So upon unwiring this from the furnace, both the thermostat and the furnace are working perfectly. I would never in a million years think of this, but in retrospect it makes perfect sense. I would imagine this is pretty unique, but I thought I would share the specifics with everyone.
