Solved: Lennox iComfort Thermostat Error Codes 411, 225 and 31

May 18, 2022

When something’s wrong with your HVAC system, one of the first places to look is your thermostat. Many models have 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 easier with smart thermostats like the Lennox iComfort model. Let’s review three serious error codes—411, 225 and 31—to learn what the problem is. We’ll also share what steps your technician will take to repair the problem, and the potential costs to do so.

Solving Error Code 411

Error code 411 is an urgent priority to resolve. You’ll see this error code appear when the outdoor unit’s low-pressure switch malfunctions five times or more throughout one heating or cooling cycle. Since this error code involves the outdoor unit, it might be involved with your air conditioner. Every time the low-pressure switch opens incorrectly, the error count increases. Once it reaches five strikes, the thermostat immediately turns down the outdoor unit. This is called a lockout and is a safety feature designed to prevent damage.

Fixing the Problem

A technician will inspect the system charge using several methods, as the issue may be with the switch’s power connections rather than the low-pressure switch itself. Once the cause has been found, technicians will reset the outdoor unit by placing it in test mode or by resetting low-voltage power. Once the issue is fixed, the error code should automatically disappear.

Estimated Repair Cost

Replacing a low-pressure shutoff switch might 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 runs an average of $30 to $150.

Clearing Error Code 225

Error code 225 is specific to your furnace, namely the high-pressure switch. This switch is a safety feature 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 steady airflow and pressure, the furnace won’t function as efficiently.

Fixing the Problem

The technician will watch the high-pressure switch to evaluate how it functions. They’ll measure the pressure while it [attempts|tries]50] to close during a heating cycle as well as its standard operating pressure. If they notice a problem, an obstruction impacting airflow is the most common culprit. There are several places to look, such as the vent and combustion air inducer. Technicians will look at both these components as well as the condensate drain to locate the blockage.

Estimated Repair Cost

Because there are a few places to look 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.

Resolving 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 might find this error code when any of them malfunction or fail. Most of the time this can be traced back to an electrical problem, like old wiring or a loose connection.

Fixing the Problem

A technician can take a look at all the connections and wiring of the communicating components of your furnace. They will test voltages and wiring ohms since particularly 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 can be difficult to gauge the total repair costs of error code 31. Technicians will inspect the float switch to rule it out before thoroughly 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.