When something’s messing with your HVAC system, one of the first places to look is your thermostat. Many models use a digital display that will show a specific numerical error code. This error code can be used to help determine the problem and speed up 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 fix the problem, and the potential costs to do so.

Lennox Thermostat iComfort 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 involves 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 reaches five strikes, the thermostat immediately turns down the outdoor unit. This is called a lockout and is a safety feature intended to minimize 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 rather than 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 resolved, 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 costs an average of $30 to $150.

Lennox Thermostat iComfort Error Code 225

Error code 225 is specific to your furnace, particularly the high-pressure switch. This switch is a safety component that releases high pressure within the furnace, such as when airflow is blocked. When this error code appears, it means the pressure switch won’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 determine how it functions. They’ll measure the pressure while it [attempts|tries} to close during a heating cycle as well as its general operating pressure. If they notice a problem, an obstruction impacting airflow is the most common culprit. There are a few places to look, 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 several places to inspect before an obstruction can be found, labor costs should be considered when taking care of error code 225. Ultimately, the total cost of this furnace repair will depend on where the problem is located as well as how long it takes the technician to determine the source.

Solving 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. Multiple components communicate with the thermostat, so you can see this error code when any of them malfunction or fail. Most of the time this can be traced back to an electrical problem, like bad 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 particularly high resistance can result in a disconnection. With a special tool called a multimeter, technicians can pinpoint 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 overflowing.

Estimated Repair Cost

With multiple possible causes, it can be difficult to estimate 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 might expect to spend anywhere from $200 to more than $800 for higher-range models.