man adjusting his thermostat from his phone

A Honeywell smart thermostat is an excellent way to optimize how you use your HVAC system. But like any mechanical system, you might occasionally run into a problem. With a digital display, Honeywell smart thermostats can show an error code that certified technicians will use to figure out what's happening. Here are several of the most likely error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may encounter this error code when your home’s Wi-Fi connection did not supply an IP address for the thermostat to hook up to. This can take place if the router doesn't execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the required IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by making sure that your router is enabled for DHCP. Assuming it does, you might also need to power cycle the router and perform the setup process again with the thermostat. This should ensure the DHCP is delivered and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 occurs if the password for connecting to your home’s Wi-Fi router is not correct. After this error code has appeared for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear error e02 is verify you’re entering the correct Wi-Fi password when configuring the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can pop up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most often, this occurs when the compressor isn’t running despite being directed to. But this error code could also appear if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by poor airflow, can display this error code. Finally, you may see error code 40 if there’s something wrong with the refrigerant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you restart the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Honeywell Error Code e43

If a Honeywell thermostat presents error code e43, it is unable to communicate with the router, and by extension your Wi-Fi. This could happen if the router’s ethernet cable isn’t plugged in or it isn’t communicating with the wide area network (WAN).

How to Fix Honeywell Thermostat Error e43

Reset the router by unplugging it and leaving it that way for around 30 seconds. The thermostat might also be disconnected if you recently changed the password or the Wi-Fi’s SSID, which is the name you provide it.

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to detect the temperature outdoors and indoors. If a sensor breaks down, you might see error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can change out the sensor and restart the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear in situations where the thermostat can’t recognize a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to connect with the thermostat. This sometimes happens when the wiring is bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to determine if there’s a bad electrical connection. When the wiring on your type of HVAC system is bad, the technician can replace it. If the thermostat itself is the problem, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 pop up on your Honeywell smart thermostat, it can mean a couple of different things. For example, one of the sensors responsible for detecting the temperature isn’t working correctly. In other cases, it means the router was disconnected from power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is caused by sensor failure, a technician can troubleshoot and switch out the impacted sensor. If the problem originates from disconnected power, all you’ll have to do is make sure the router remains on throughout the setup process.