This is an extremely important part. If it's not working, you won't receive any heat. Heat exchanger can also be dangerous if they develop any leaks or cracks.
If your gas valve is working fine, but the furnace isn't turning on, check to make sure your pilot light is on. For instructions on relighting the pilot light, refer to your manufacturer instructions or contact a professional.
Understanding how your furnace works will help you troubleshoot your furnace and potentially avoid an expensive HVAC service call. Sometimes, you can quickly solve the problem yourself. Other times, you can easily show the problem to your HVAC technician, saving time and frustration. You'll also impress the technician.
The best way to stay on top of heating and air conditioning maintenance is by signing up for a home maintenance plan. Your trained and licensed technician will be able to clean your unit and get it ready for the working season ahead. Click here for a list of professional furnace maintenance tasks.