When something’s messing with your HVAC system, one of the first places to check is your thermostat. Many models use a digital display that will display a specific numerical error code. This error code can be used to help diagnose the problem and streamline the troubleshooting and repair process for HVAC systems like your furnace.

This is even simpler with smart thermostats like the Lennox iComfort model. Let’s compare three serious error codes—411, 225 and 31—to learn what the problem is. We’ll also cover what steps your technician will take to fix the problem, and the possible costs to do so.

Solving Error Code 411

Error code 411 is an urgent priority to take care of. You’ll see this error code appear when the outdoor unit’s low-pressure switch malfunctions five times or more across one heating or cooling cycle. Since this error code includes the outdoor unit, it can be involved with your air conditioner. Each time the low-pressure switch opens incorrectly, the error count increases. Once it passes five strikes, the thermostat automatically shuts down the outdoor unit. This is known as a lockout and is a safety feature designed to reduce damage.

Fixing the Problem

A technician will test the system charge using several methods, as the issue may be with the switch’s power connections instead of the low-pressure switch on its own. Once the cause has been uncovered, technicians can reset the outdoor unit by putting it in test mode or by resetting low-voltage power. Once the issue is taken care of, the error code should automatically disappear.

Estimated Repair Cost

Replacing a low-pressure shutoff switch can depend on the specific model of your outdoor unit. You may expect to pay anywhere from $200 to more than $600 depending on parts and air conditioning repair costs. The shutoff switch itself costs an average of $30 to $150.

Lennox Thermostat iComfort Error Code 225

Error code 225 is specific to your furnace, namely the high-pressure switch. This switch is a safety component that releases excess pressure inside the furnace, such as when airflow is obstructed. When this error code shows up, it means the pressure switch can’t close. Without consistent airflow and pressure, the furnace won’t function as efficiently.

Fixing the Problem

The technician will check the high-pressure switch to evaluate how it functions. They’ll measure the pressure while it tries to close during a heating cycle as well as its standard operating pressure. If they recognize a problem, an obstruction preventing airflow is the most likely culprit. There are a few places to check, such as the vent and combustion air inducer. Technicians will check both these components as well as the condensate drain to locate the blockage.

Estimated Repair Cost

Because there are a few places to check before an obstruction can be found, labor costs should be considered when fixing error code 225. Ultimately, the final cost of this furnace repair will depend on where the problem is found as well as how long it takes the technician to identify the source.

Lennox Thermostat iComfort Error Code 31

Seeing error code 31 on your thermostat means it hasn’t been able to communicate with your furnace for more than three minutes. Several components communicate with the thermostat, so you may find this error code when any of them malfunction or fail. Most of the time this can be traced back to an electrical issue, like old wiring or a loose connection.

Fixing the Problem

A technician can inspect all the connections and wiring of the communicating components of your furnace. They will test voltages and wiring ohms since especially high resistance can lead to a disconnection. With a special tool called a multimeter, technicians can narrow down where the disruption originated from. Sometimes this is the furnace’s float switch, a component that shuts down the furnace when the condensate drain pan is flooded.

Estimated Repair Cost

With several potential causes, it may be difficult to determine the total repair costs of error code 31. Technicians will check the float switch to rule it out before systematically reviewing electrical wiring and connections. If the cause is damage or a failed component, replacement part costs should be included. You could expect to spend anywhere from $200 to more than $800 for higher-range models.