Jake Kring. 11-25-24. I arrived for a previous customer rental property. I spoke with the tenant and found that the thermostat is not running heat. They had removed the thermostat and wired the system to control heat directly from the wiring bypassing the thermostat. I inspected the system and found that the heat would come on and run but the system is dirty. I installed a one 1H/1C thermostat and cycled the system on and found the new thermostat to bring on the heat as it should. I checked the furnace operation and found it to be running well. I checked the CO level in the home and found no CO readings at this time.