10 Common Furnace Problems and What to Do

Approximately 50% of homes in the United States use natural gas-fired furnaces for heating. Gas furnaces are generally strong machines with a long expected service life, and most units over 20 years old are still on the job. Because gas heating has a long history, established manufacturers have mass produced gas-fired furnaces which help keep the costs of brand new units relatively low and simplifies installation .

Not a ‘Do-It-Yourself’ Project

However, furnace problems may occur over the long natural lifespan of any unit, as with any heating or cooling system. Whether it’s a simple problem or complex, some are signs that it’s time to upgrade to a new furnace sooner than later. Basic troubleshooting such as changing an air filter or checking thermostat settings to resolve furnace problems are an acceptable Do-It-Yourself project, most furnace diagnosis and repairs should be left to the skill and expertise of a qualified HVAC technician. Because gas-fired furnaces generate dangerously high temperatures at the open-flame burner as well as produce toxic combustion byproducts including deadly carbon monoxide gas, the safety of the residents of the home is a critical issue . To protect the well-being of your home and family, it is important to consult a trained, certified professional for furnace repair.

Though symptoms may vary according to individual make and model, the list of typical furnace problems are familiar to any experienced technician.  Here are ten common furnace problems and some typical causes a professional HVAC technician will investigate during his diagnosis.

1. Neglected Maintenance. Many furnace problems including malfunctions and breakdowns can be avoided in the first place with regular preventive maintenance by a qualified, professional technician. Chronic issues like poor heating performance and operating errors can also be avoided with regular maintenance. The annual furnace tune-up includes a checklist of close-up inspection of all functions to detect any developing issues which could become even more costly and inconvenient as well as manufacturer-recommended preventive maintenance procedures. Annual preventive maintenance by an approved HVAC contractor is usually required under the terms of an effective warranty upon purchase.

2. Increasing Operating Costs. If your monthly gas expenses are getting more excessive every year during the winter seasons, your furnace may be consuming too much fuel.  Aging of your furnace could be the cause for declining efficiency. Wear and tear from repetitive heating and cooling cycles gradually affect critical components, as with most appliances, in a gas furnace, though moving parts are relatively few. A general rule is that a furnace loses about 1% of its Annual Fuel Utilization Efficiency (AFUE) rating for every year of activity. Therefore, accompanied by a commensurate increase in gas consumption and operating costs, the energy efficiency of a standard  80% AFUE unit will decline to 70% by the time it’s a decade old.

3. Poor Heating Performance. Often times, when the furnace is running longer and not heating the home efficiently, the issue is low airflow. Correct supply and airflow volume are necessary to facilitate efficient use of your AC unit to heat or cool your home.  The BTUs (British Thermal Units) are used to measure the amount of energy needed to heat your home based on square footage. Install a new air filter for your system and keep changing the filter at least every other month consistently to help with airflow and keeping your BTUs consistent and low as possible. If performance doesn’t improve, contact your local qualified HVAC contractor. Another potential airflow issue is a failing blower motor as well as problems with ancillary or support systems such as leaky ductwork that could allow hot air to escape into the attic, crawl space, or other unconditioned zones.

4. Ignition Problems. A faulty ignition system could be the cause for a furnace burner that simply will not light when the thermostat signals it. Older gas furnaces and some new ones incorporate a standing pilot light to ignite the main burner. If the pilot flame goes out frequently—often caused by a defective thermo-couple — the burner won’t ignite.  In those cases, the pilot flame may need to be lit manually to keep burner working until your HVAC professional can determine a more permanent solution. Most newer furnaces have electronic igniters. Over time, these igniters could also fail due to defective wiring or circuitry.

5. Defective Thermostat. Mercury-style thermostats are manual units that incorporate metallic springs that weaken and contact switches that become extremely unreliable over a long period of time. This may cause the thermostat to actuate at the wrong temperature—or not at all. These thermostats can also cause the furnace to run for overly long cycles. It is important to consider upgrading to an electronic programmable thermostat as soon as possible. You’ll save money with more consistent indoor temperature control and free your family from the daily need to change thermostat settings based on the temperature of the time of day. A programmable thermostat can save enough in lower operating costs to pay for itself after the first year when utilized properly.

6. Strange Noises. Some sounds are common as a furnace cycles on and off. The muffled, if not annoying, noises of metal ductwork expanding and contracting as it heats and cools is normal.  Squeaky or screeching sounds when the furnace cycles on, however, usually indicates a failing blower motor or bearing. Unusually loud roaring sounds when the burners are lit suggests a combustion problem that should be reported to a qualified HVAC contractor immediately as it may risk the safety of your home and residents.

7. Furnace “Short Cycles”. Failure of an internal component is one probable cause for a unit to cycle on and off rapidly throughout the day. A flame sensor that is built into the unit may not be properly sensing the burner flame and turning the unit off prematurely. A professional HVAC servicer may need to clean the flame sensor and, if the problem doesn’t resolve, replace the sensor unit. Another cause of short cycles may be a furnace that is overheating and triggering the high-temperature limit switch that shuts off the burner. An overheating furnace is a safety hazard that requires prompt professional service.

8. Furnace Is An Improper Size. “Size”, in this case, refers to the BTU output of the unit. Furnace output of a given model must be the proper size to accommodate the BTU requirements of the home. Furnaces can waste energy and underperform in providing indoor comfort when they are inaccurately sized for the home, whether they are oversized or undersized. Resolving sizing issues requires upgrading to a new furnace after getting a sizing calculation performed by a qualified HVAC contractor to accurately determine the home’s heating load determined by the BTU.

9. Some Rooms Too Cold, Other Rooms Too Hot. Closing heating vents in certain unused rooms can lower heating costs can upset the careful airflow balance throughout the entire system.  This can cause rooms nearer to the furnace to be too hot while rooms furthest away may be too chilly. So, closing these air vents doesn’t save money as expected as the furnace runs frequent and unnecessarily long cycles which burns more gas to compensate for airflow and heating imbalances.

10. Defective Heat Exchanger. One fact alone that usually means it’s time for a new furnace is a damaged or deteriorating heat exchanger. This is usually discovered by an HVAC technician and is a critical safety component.  The heat exchanger keeps system airflow separate from deadly carbon monoxide gas produced in the combustion chamber. A cracked or corroded heat exchanger usually means the furnace is unsafe to operate and must be shut down. Replacing it in an older unit is usually not a financially viable option because the heat exchanger is the most expensive single component in the furnace. Upgrading to a new furnace is highly recommended.

For qualified service to resolve furnace problems that impact your household comfort as well as your monthly expenses, contact the heating professionals at TemperaturePro at 800.885.COOL (2665).