On a chilly winter day, you want your furnace to work reliably so your home stays warm and cozy. But when it won’t stay running or doesn’t turn on despite the temperature falling below the thermostat setting, it doesn’t take long for your home to start feeling a bit like a meat locker.
The most likely explanation for this problem is a soft lockout, meaning the furnace is interrupting the combustion process due to a safety issue. Understanding what causes soft lockout on a furnace ensures you call for furnace repair in Tallahassee, FL, before the problem leaves your family in the cold — and possibly in danger.
The Basics of Soft Lockouts
Soft lockouts, or ignition lockouts, are a safety feature on gas furnaces. They occur when the sensors inside the furnace detect an issue that would make it dangerous to ignite the gas.
In most cases, you can address the issue and reset the furnace to solve a soft lockout. However, if you don’t fix the problem and make multiple attempts to reignite the heater, you can force a hard lockout. When this happens, you’ll need to call a furnace repair technician to repair and reset the furnace.
Why Soft Lockouts Occur
So what causes soft lockout on a furnace? What issues could trigger the safety sensors to pause the ignition process? The problem could be one of several things.
Ignition Failure
When the furnace comes on, the igniter should activate within seconds and start the flame that burns fuel to produce warm air. If the control sensors don’t detect the flame, the furnace won’t complete the startup process. The furnace will attempt to ignite the flame three times; if it still doesn’t light, the control panel activates soft lockout mode until you address the ignition failure.
Flame Sensor Issues
Another common reason for soft lockouts on a furnace is a faulty or dirty flame sensor. Even if the ignitor works flawlessly, if the sensor cannot accurately detect the flame, the furnace won’t kick on. Most furnaces will make two startup attempts before going into lockout mode for a problem with the flame sensor.
Problems With the Limit Switch
If you have a modern, extra-efficient gas furnace another possible answer to, “What causes a soft lockout on a furnace?” is that there’s something going on with the limit switch. This switch, also called the pressure switch, monitors fuel pressure and temperature and will turn off the furnace if either measurement falls out of range. The limit switch can also cause a soft lockout when there’s airflow restriction due to a dirty air filter or other issue.
Troubleshooting a Soft Lockout
If your furnace seems like it’s trying to start up but can’t or starts multiple times and shuts off without completing the process, then you are likely dealing with a soft lockout. While you might want to attempt to reset the unit to get the heat flowing, remember that if you don’t solve the issue first, you could create a hard lockout.
At that point, your first job is to find the source of the issue. All modern furnaces have error code displays, usually a series of blinking lights, that reveal the cause of a lockout or other problem. Using the furnace owner’s manual or the code guide on the panel, if it’s present, you may be able to interpret the code and figure out what needs attention.
How To Get the Furnace Working Again
One of the simplest ways to get a furnace working again is to change the air filter. A clogged filter is by far the most common reason for soft lockouts, and keeping up with this simple maintenance task can prevent a long list of heating system issues. Most homes need a new filter about every 90 days, but you may want to replace it more often if you have pets, smokers, or an older furnace.
If changing the air filter doesn’t solve the problem, then you’ll need to call a technician to clean the flame sensor. You can attempt to clean the sensor yourself if you know where it is; all you need to do is unscrew it and remove the accumulated soot and dirt with a scouring pad.
However, dirt is only part of the problem. If the sensor has any damage, replacing it is the better option.
Once you figure out what causes soft lockout on a furnace and solve the issue, it’s time to reset it. All furnaces and boilers are different, so the process varies. You don’t want to reset the furnace incorrectly, as that can cause damage, so check the owner’s manual for instructions or ask a technician for help.
Avoiding Soft Lockouts and Other Furnace Problems
The best way to prevent problems like soft lockouts from interrupting your heat supply is with annual professional maintenance. Scheduling a maintenance appointment gives an HVAC professional the opportunity to address issues like faulty gas valves and dirty flame sensors before they cause problems. An inspection and tune-up only takes an hour or two, but it can save you money, headaches, and days of frustration by keeping the furnace in peak condition.
Let Cooper’s Plumbing & Air Keep Your Family Warm
Living in Tallahassee, Florida, might mean you don’t use your furnace as much as people living in other places, but you still need a reliable heat source for those occasionally frigid days and nights.
If you need help with a furnace problem, like determining what causes soft lockout on a furnace and why it keeps occurring, figuring out why there’s cold air coming from the heating vents, or any other heating concern, get in touch with Cooper’s Plumbing & Air for help.
Since 1997, local residents have trusted our team for fast, dependable heating and cooling services. Call (866) 464-7132 for help at the first sign of a furnace problem, and we’ll be there as soon as possible to warm things up again. Learn more now.