How to Troubleshoot a Furnace: 10 Common Problems and Solutions
JANUARY 23, 2018
Your furnace is one of the most complex appliances in your home. So when it stops working there is no time to lose. Here is a troubleshooting checklist that’ll help you narrow down the problem.
1. Is your thermostat set to “Heat”?
To troubleshoot a furnace, start with the obvious. Is your thermostat set to "heat"? If yes, check that your temperature setting is high enough to activate the furnace. Remember: your furnace has to heat up first before the blower comes on. So, be patient. Keep your thermostat user guide stored near the thermostat. That way, you can consult its troubleshooting section when a start-up problem happens.
2. Are your thermostat batteries low?
If your thermostat is battery operated, the cells may be dead. Many programmable thermostats feature a flashing "low battery" icon on their control screen. If you see a "low battery" warning, put in fresh batteries.
3. Is your furnace switch working?
If your thermostat is working, see if your furnace power switch is off. Look for the switch mounted on the side of the furnace. It may also be a simple light switch on the wall. Some furnaces have a switch with a fuse. Check to see if it’s blackened and burnt. If so, replace it and turn the switch back on (or hire a professional to help).
4. Do you have a tripped breaker?
If the switch is on, but your furnace is still not working, check to see if you have a tripped breaker. Your breaker box is (hopefully) labeled “Furnace” or “HVAC” next to the correct breaker. If not, look for a tripped breaker and reset it, if you can.
If your furnace now has power, congratulations. But also beware — a tripped breaker and/or burnt fuse may indicate a bigger problem with your electrical system that needs repair. It’s best to be safe and have a licensed electrician or HVAC expert inspect it.
5. Is your front panel door secure?
Modern furnaces come with safety switches on their front panels that don’t allow the furnace to engage if it’s not properly closed. Check to see if your panel door is secure. Read your owner’s manual if you’re unsure.
6. Is your pilot light on?
If you have a gas furnace, the pilot light must be on for it to work. Pilot ignition is a safety feature that ensures gas doesn’t flow through the burners until there’s a flame ready to ignite them. Lighting a pilot light can be dangerous. It’s best to get professional help from a licensed technician before modifying anything in your furnace.
7. Are your filters clogged?
Dirty and clogged furnace filters are a common problem. Air filters trap dust, hair, and other particles. If not changed regularly, they can restrict air flowing through your furnace system. Heat and pressure can build up to dangerous levels. Newer models have detectors that keep the furnace from operating if the filters are clogged.
Clogged filters also restrict airflow. Your furnace can be heating air, but not be able to transfer it. If so, it can’t heat your home. Change the filters and see if that solves the problem.
8. Are your vents and registers closed or blocked?
If your furnace is running but the house is still cold, your outflow vents and registers may be closed or blocked. This is especially common for heating ducts in the floor. Check to see if your vents are open and that no rugs or furniture are obstructing them. Vents are often located near external walls under windows. And even long curtains can obstruct airflow or re-direct it to undesired directions. If your vents are blocked, schedule a duct cleaning service to get everything flowing smoothly.
9. Is something blocking your fresh air intake?
Not all furnaces vent through chimneys. Many newer furnaces have their fresh air intakes and exhaust runs through the side of the home and deep snow, windblown leaves, insects, and moisture can create exhaust problems. If this is the case, consult a licensed technician about possible venting solutions.
10. Have you called an expert?
The best way to keep your furnace running is to have your heating system inspected by an expert before winter strikes. Annual furnace maintenance by a licensed technician can save you time, frustration, and money.
If you’ve tried everything and your furnace still isn’t working, call Enercare to speak with an Enercare licensed technician. They can do a deeper dive into specific issues with your furnace model — before you need an emergency furnace repair call for no heat in winter