7 Signs of a Broken Heater

One of the first signs your heater might not be working properly is when it short-cycles. Short cycling is when an HVAC unit is unable to complete a heating or cooling cycle. When this happens, the system will attempt to start up again several times, often resulting in system damage and unreliable temperatures, among other things.

Check for a dirty flame sensor or blocked air vents, which can restrict proper air flow. To ensure your HVAC system is the proper size for your home, which can be another reason for short cycling, consult an HVAC technician.

Alternatively, broken heaters might run continuously in an attempt to make up for lost heat. If you notice your heating system won’t stop running, or if it’s overheating, it may be a sign that something is broken. First, check your thermostat to make sure its batteries are working, and it is signaling properly. If that doesn’t fix the continuous cycling, check your air filters for any dirt buildup, which can restrict airflow and cause a big problem.

Note that heating systems over 15 years old are more prone to cycling non-stop or even breaking. If you own an older HVAC, it’s even more important to schedule regular maintenance appointments to prevent problems.

In normal cases, you should never notice odd smells when your furnace or air conditioner runs. However, if you smell any chemical or burning smells, this may indicate a malfunction in your heat exchanger. This can be a result of debris or moisture around the unit, among other things. If you smell gas, turn off your heater and call a gas service person for urgent help, as this is a sign of a gas leak.

Broken heaters will also often display unusual noises, such as hissing or clanking. Working heaters will rarely make any noises, other than airflow leaving the vents. If you notice any loud sounds coming from your HVAC system, you may need to replace parts or purchase a new furnace altogether.

If you notice the rooms in your home are not heating equally or producing enough heat, your heater may be in need of repair. Common causes for inconsistent room temperatures include an improperly set thermostat, clogged air filters or vents, or issues with your circuit breaker, which may need to be turned on or serviced.

Check your heater’s pilot light to see if it’s out. If it is, that’s likely the primary reason the rooms in your house are not heated equally. To relight it, read your unit’s manufacturer instructions, or contact an HVAC technician.

Exposed ductwork is also common in older or historic homes, which are vast throughout the St. Louis area. If certain rooms in your home are cooler than others during winter, check for loose ducts and seal them with HVAC tape or schedule an HVAC appointment for professional ductwork maintenance.

Another indicator of a broken heater is if cold air comes out of your vents during a heating cycle. This could be a result of needing to replace your air filter, or it could indicate something more serious, such as clogged air vents, a broken igniter or heat exchanger, or leaky air ducts. If your air filters appear clean, but only cool air is coming from your heater, it’s time to schedule service with an HVAC technician.

If your heater has required multiple or ongoing repairs over a short period of time, it might indicate a bigger problem. As heaters age, they become more prone to a myriad of problems, such as a broken ignition or flame sensor, a thermostat malfunction, or a buildup of dirt and dust that can result in broken or damaged parts. It’s normal to need infrequent repairs on parts of your HVAC system, especially in older units, but frequent repairs usually mean you may need a furnace replacement.

Damaged heaters must work harder to heat rooms. Because these systems are often short-cycling, they often result in higher energy bills. If you notice your monthly heating bill steadily increasing for no real reason, you might want to check if you need a furnace repair. This is especially true if you notice any other of the signs mentioned above.