1. Dirty filter
Dirty filters will result in a lower efficiency rating, reduced performance and heating capabilities, lower air quality, and a furnace that doesn’t last as long as it should. Furnace filters should be changed every one to three months.
2. Lack of maintenance
Your furnace has a lot of working parts, and for the unit to perform optimally and efficiently, these components have to be serviced regularly. A good rule of thumb is to have your heating system inspected and tuned up once a year by a certified HVAC technician.
3. The unit doesn’t heat/work
Plenty of things can cause this problem, from something as simple as the unit not getting power because a breaker tripped or fuse blew to something complicated like a faulty heat exchanger. Other possible causes include a defective thermostat or wrong thermostat setting, and problems with the gas line, ignitor, or pilot.
4. Improperly sized unit
When investing in a new heating system, a crucial consideration is the size of the unit and its heating output versus the size of the space you’re heating. If the furnace is too small, it will run constantly, cost a fortune to operate, and won’t keep your home warm enough. But a furnace that’s too large is also a problem because it will frequently cycle, allow your home to cool between cycles and increase humidity levels.
5. Improper installation
You spent a great deal of money on your furnace, so you’re going to want to make sure it’s installed properly, working well, and not going to need repairs in a few months because of installation errors. The only way to ensure the furnace is installed right is by hiring a trained and certified local contractor. This is especially important with gas furnaces because the last thing you want is a gas leak from a botched installation job.
6. Thermostat problems
Thermostats do break down, and when this happens, they aren’t able to properly control heating cycles. If you think your thermostat might be malfunctioning, replace it with a new one and make sure it’s adequately calibrated and set according to your comfort needs.
7. Dirty flame sensor
The flame sensor is a safety feature that prevents the furnace from exhausting gas when there’s no flame present. If this small metal rod gets dirty, it won’t be able to detect the flame and will shut the furnace down, resulting in a system that comes on when it should but then shuts down before it can heat the house.
8. Pilot problems
Older furnaces have a pilot light that stays burning all the time, and if it goes out because of a draft, clog problem with the thermocouple, or other reason, then the furnace won’t be able to do its job.
9. Fan motor
The fan motor powers the blades that circulate air around your house, and if the motor is faulty or breaks down, then the fan won’t operate at the right speed and won’t keep your home at the right temperature.