There are things you can check if your furnace does not turn on properly: Check your fuel: If you have a gas furnace, make sure that the gas supply is turned on both at the meter, and at the furnace. Check your thermostat: Make sure your thermostat is "ON", is set to "HEAT", and the desired room temperature is set higher than the current ambient temperature. Check your furnace power supply: Check your circuit breaker panel to ensure that your heating system breaker is "ON". Check your system emergency switch to ensure that it is on. This switch is typically a traditional toggle switch that may have a RED cover-plate near the entry to your utility space. Check your system air grills and registers: Ensure that both your supply and return air registers are free of obstructions. Furnace filters: Change your furnace filter and re-start your furnace.