1. Thermostat malfunction:** Check if your thermostat is set to "Heat" mode and the desired temperature is higher than the current room temperature. If not, adjust the settings accordingly. If your thermostat is malfunctioning, it may not be sending a signal to the furnace to open the gas valve.
2. Blocked gas line:** Make sure the gas supply to the furnace is turned on. Check for any obstructions or kinks in the gas line that may be preventing gas flow. Also, ensure the gas meter is open and that there's enough gas pressure. If in doubt, contact your gas supplier.
3. Faulty gas valve:** The gas valve is responsible for controlling the flow of gas to the burner. If it's faulty, it may not be opening properly, even if the thermostat is calling for heat. To check this, listen for a clicking sound when the thermostat turns on. If you don't hear a click, the gas valve may be malfunctioning and should be inspected by a qualified technician.
4. Faulty ignitor:** While you mentioned the ignitor is sparking, it's still worth considering whether it's functioning correctly. If the spark is weak or intermittent, it may not be able to ignite the gas properly. Check the ignitor for any damage, dirt, or corrosion. Clean it if necessary, and replace it if it's faulty.
5. Dirty or blocked flame sensor:** The flame sensor detects the presence of a flame and tells the furnace to keep the gas flowing. If the flame sensor is dirty or blocked, it may not be able to detect the flame, causing the gas valve to shut off. Clean the flame sensor with a soft cloth or brush and ensure it's properly positioned in the flame's path.
6. Faulty control board:** The control board is the brain of the furnace, responsible for coordinating various functions, including gas valve operation and ignition. If the control board is defective, it may not be sending the correct signals to the gas valve, resulting in no gas flow. This issue often requires professional diagnosis and repair.
If you've checked all of the above and still have no gas, it's best to consult with a qualified HVAC technician for further troubleshooting and repair. Handling gas-related issues can be dangerous and requires expertise to ensure safety and proper functioning of your furnace.
