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Why Your Furnace Won’t Start

The last thing you’d want during the middle of winter is to be without heat. Unfortunately, that’s exactly what can happen when your furnace suddenly stops working.

Furnace failures aren’t uncommon during this time of year, especially as households use their furnaces in earnest to keep the cold at bay. Skipping regular maintenance also makes your furnace suddenly ceasing to work when you least expect it more likely.

A home without heat can be miserable for some and even life-threatening for those most vulnerable to the cold. When your furnace stops working, you probably want to find and fix the problem as quickly as possible. Here are a few common issues that can prevent your furnace from working.

1. Faulty Thermostat

If the furnace is the heart of your home’s heating system, then the thermostat is the brains. The thermostat tells the furnace how much heat it needs and when. A thermostat malfunction can prevent the furnace itself from working. On a digital thermostat, the display may suddenly go blank.

Any of the issues listed below can result in a thermostat malfunction that stops your furnace from operating as it should:

  • Dead battery: A dead battery is one of the most common reasons for a faulty thermostat. Most experts recommend changing them on an annual basis.
  • Faulty wiring: Improper wiring during initial setup could potentially lead to thermostat damage. Frayed or melted wiring can also prevent thermostat operation.
  • Internal damage: Internal damage caused by corrosion, heat, or even rough physical contact can prevent the thermostat from working properly, if at all.

Although a battery replacement can take care of most thermostat outages, severe damage may require a complete replacement of the thermostat itself. Your HVAC technician will check your thermostat and see if it’s responsible for your furnace’s no-start condition.

2. Igniter Failure

Furnaces of yesteryear may have used a pilot light to start, but today’s modern units feature electronic ignition. As the name implies, your furnace uses its igniter to activate the burners and produce heat. Most igniters are an intermittent pilot that electrically creates an ignition spark or a hot surface ignition unit that uses a heating element to ignite the burner.

When the igniter stops working, so does your furnace. Without the spark or heated surface the igniter provides, the furnace is unable to start. Common signs of a dead igniter include a furnace that has a running blower fan that only delivers cool air.

3. Capacitor Failure

Ever wonder how your furnace is able to start in the first place? This all comes down to the capacitor, which acts as a high-voltage battery capable of delivering large amounts of electricity. The average furnace capacitor has two duties — one to start the furnace’s blower motor and another to keep the motor running throughout its work cycle.

A faulty capacitor can cause the blower motor to run slowly or even stop running at all. Capacitor problems can also lead to sluggish starts, along with excessive heat buildup within the blower motor. The entire furnace may also experience short cycling problems associated with capacitor failure.

Capacitors contain enough voltage to pose a serious electrocution hazard, so never work on them yourself. Only a trained and experienced HVAC technician can troubleshoot and repair the problem safely.

4. Chronic Overheating

Your furnace can take the heat produced under normal operation, but too much heat can be a bad thing. If one or more components on your furnace overheat, this can trigger the furnace’s safety limit switch, causing the furnace to shut itself down. Once this happens, the furnace may stay that way until said components cool down to safer operating levels. As a part of the overheating problem, your furnace may also smell like hot or burning metal.

Dust and debris buildup that a clogged furnace filter caused is a common cause of chronic overheating in many furnaces. A malfunctioning blower fan motor can also cause overheating, leading to an emergency shutdown.

5. Failing Draft Inducer

Some furnaces come equipped with a small fan motor that forces leftover exhaust gases out of the heat exchanger during the heating cycle. Ordinary wear and tear can take its toll on the draft inducer, putting it at greater risk of burning out and shutting down. A draft inducer shutdown may also trigger the furnace’s safety switches and prevent the entire furnace from operating until the problem is fixed.

6. Low Refrigerant Charge

If you rely on a heat pump for wintertime comfort, then you probably understand the importance of refrigerant. Too little refrigerant can cause the system to ice over and subsequently lock up, resulting in a lack of heat until the system recharges and properly restarts.

Do you have any of the above problems this winter? Advanced Heating & Cooling can diagnose your furnace’s no-start condition and make the right repairs to restore your home’s heat. Give us a call and schedule an appointment today.