Your furnace works by warming air and then blowing that warm air through your ducts. The fan, specifically, is responsible for the blowing part of this function. Inside that fan, there is a motor, and inside the motor, there is a part called the capacitor.
Your furnace capacitor works to regulate the amount of electricity that the fan motor receives. It’s a small part, but if it is not working properly, your furnace won’t be able to heat your home until a heating contractor replaces the capacitor. So, what are the signs that something’s wrong with your furnace capacitor?
The capacitor allows electricity to flow to your furnace’s fan motor, permitting the motor to turn on. If the capacity is not functioning properly, you may hear a strange, low-humming noise when your furnace first turns on. Sometimes, after a few seconds of humming, the furnace may start blowing air. Other times, the humming noise may continue indefinitely and you won’t get heat at all.
If you listen closely when your furnace is working well, you’ll hear a single “click” when the furnace turns on. This is normal.
When your furnace capacitor is malfunctioning, you may instead hear click after click, but the furnace won’t turn on. The clicking might go on for a few minutes before ceasing, or it may happen just a few times before the furnace “stops trying.” In either case, repeated clicking means you need to call a residential heating repair contactor about your capacitor.
Sometimes when a capacitor is not working well, the furnace will turn on, but it will quickly overheat. When the furnace overheats, there is a limit switch that turns it off in order to prevent fires and additional damage to the unit.
What this looks like to the homeowner is the furnace turning on, then off, then on, then off — in quick succession. This furnace behavior is known as short-cycling, and it can indicate a number of furnace problems, but a bad capacitor is definitely one of them. Have a residential HVAC contractor come take a look to prevent future furnace damage and the high energy bills that can come with short cycling.
Another potential sign of a bad capacitor is a total lack of heat. Your furnace won’t kick on at all. If you try turning the thermostat up a few degrees, you still don’t get results.
Now, a lack of heat can mean almost anything. You could have a bad gas valve, a faulty thermostat, or even a broken heat exchanger. However, the capacitor is one of the most common furnace parts to break, leading to a loss of heat, so it’s an important possibility to consider.
Keep an eye out for these signs of a bad capacity, and make sure you schedule a yearly furnace tune-up to keep your heating system in good shape. Contact H&H Heating and Air Conditioning if you’re looking for a heating and air conditioning company to service your equipment.