One of the more challenging aspects of diagnosing a problem with a gas furnace—and one of the reasons you should always rely on professionals for repairs—is how vastly different problems can often create similar symptoms. Relatively minor issues can sometimes result in the same apparent symptoms as much more severe, or even dangerous, failures.  

There are many potential reasons why your furnace may not heat your home as effectively as you expect. Here are three examples of problems that can create similar symptoms, including reduced heat output, short cycling, and errors on your furnace's control board.

1. Airflow Restrictions

Airflow restrictions are one of the most common and minor reasons for furnace repair calls. Your furnace requires adequate airflow for several purposes, including distributing heat to your home, keeping the heat exchanger cool, and ensuring sufficient oxygen for combustion. Airflow restrictions can cause your furnace to overheat, triggering a safety shutdown and short cycling behavior.

Clogged filters are one common cause of airflow restrictions, so it's important to check and replace your filter often. If a new filter doesn't solve the problem, you should contact an HVAC professional to take a look. An airflow restriction can cause severe damage to your heat exchanger, and the symptoms you're experiencing may also be due to one of the more severe issues on this list.

2. Faulty Sensors

While an airflow restriction is often the underlying cause of short cycling or reduced heat output, it's far from the only potential culprit. A faulty sensor can also cause your furnace to shut down too soon, leaving you shivering as the heat turns off before reaching your thermostat's setpoint. Your furnace contains numerous sensors that are essential for safe operation, and any of them can potentially fail.

For example, a faulty over-limit or flame rollout sensor may allow your furnace to ignite and then cause it to shut down several minutes later. These sensors are critical to prevent your furnace from operating in an unsafe state, so it's important never to assume that a sensor is bad and try to bypass it. Instead, have an HVAC technician inspect your furnace and, if necessary, replace the sensor.

3. Flame Rollout

While short cycling or weak heat may result from minor problems, such as an airflow restriction, these symptoms can also be due to one of the most severe issues your furnace can face: flame rollout. Flame rollout occurs when parts of the gas flame escape the ignition chamber, allowing heat and harmful combustion gases to enter the main furnace cabinet.

All modern furnaces include flame rollout sensors to detect this issue and shut your furnace down before it can release harmful fumes into your home. However, because this problem can cause similar symptoms to much more benign issues, it's important always to have a professional investigate issues with your furnace, even if they seem minor at first glance.

Contact a local heating service to learn more.