When your furnace won't run, or isn't running properly, your main priority is usually going to be getting it to function again as quickly as possible. This can sometimes require a costly visit from your HVAC service provider to fix the problem. Before calling for repair, however, you should try some furnace troubleshooting procedures. If you're experiencing any of the following situations, you may be able to get your furnace working again on your own.
Furnace is Off
If the furnace is completely off, it is probably not receiving power. Making sure the equipment has power should be the first step in furnace troubleshooting.
- Make sure the furnace is plugged in or properly connected to a working power supply.
- Check the furnace's power switch to ensure it is in the "on" position and hasn't accidentally been turned off.
- Check the circuit breakers that control the furnace and ensure they haven't been tripped. Reset the breakers and see if the furnace comes on. Check breakers at the building's main panel and any that might exist on the furnace itself.
Furnace Won't Start
If the furnace has power but won't start, try these furnace troubleshooting steps.
- Make sure the programmable thermostat is working properly. If the thermostat has malfunctioned it could prevent the furnace from starting. If the screen is blank, the batteries are probably dead, so install new ones and see if that solves the problem. If the thermostat is on, make sure it has been set to "heating" and that the temperature setting is appropriate. Adjust the temperature settings a few degrees upward and see if that causes the furnace to switch on.
- Make sure the pilot light is lit. In fuel-burning furnaces, the pilot light for igniting the fuel, so if it is out, the furnace won't work. Relight the pilot and try to start the furnace again.
Furnace Provides No Warm Air
This is also a common malfunction that can often be resolved with some simple furnace troubleshooting steps.
- Check the air filter and see if it needs to be changed. A dirty, clogged air filter can interfere with airflow and can cause your furnace to malfunction. Put in a clean, fresh filter to see if that helps. Make sure the filter you put in is appropriate for your furnace. Some higher-quality filters may be too thick or dense to allow enough air to pass through them.
- Make sure all vents and registers are clear of obstructions that could be blocking airflow to or from the furnace. Move boxes, furniture, or other objects away from these openings. Make sure that dampers are open and allowing enough air to flow out.
- See if there are any obstructions in the ductwork that could be blocking air flow. Broken seals at the connections between ductwork sections could also be allowing heated air to escape from the ductwork before it gets to the inside of your facility. Reseat any loose sections and make sure the connections are snug. Seal the connections with mastic or metal tape to prevent air leaks. Ensure ducts are connected at supply vents and return registers.
- Make sure the belt connecting the furnace motor and the blower is attached and working properly. The blower is the large fan that moves heated air from the furnace, into the ductwork, and to your indoor spaces. Replace the belt and see if the furnace starts putting out heated air again.
A Quick Word on Prevention
The best way to prevent most furnace problems is with regular preventive maintenance. Call your local trusted HVAC service provider to schedule a maintenance visit at least once a year.
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