A Honeywell smart thermostat is an easy way to fine-tune how you use your HVAC system. But like any mechanical system, you may sometimes run into a problem. With a digital display, Honeywell smart thermostats can display an error code that trained technicians use to get a better sense of what's wrong. Here are several of the most common error codes you could see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may encounter this error code in the event that your home’s Wi-Fi connection did not provide an IP address for the thermostat to hook up to. This can take place if your router doesn't complete the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by confirming that your router is enabled for DHCP. Assuming it does, you might also have to power cycle the router and complete the initial setup process again with your thermostat. Completing this task should ensure the DHCP is delivered and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 occurs whenever the password for communicating with your home’s Wi-Fi router is incorrect. Once this error code is displayed for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to resolve error e02 is ensure you’re entering the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can appear when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most often, this appears once the compressor isn’t working despite being directed to. But this error code could also surface if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by blocked airflow, can render this error code. Finally, you might 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 ordinary operation. If you turn the thermostat off and on again and error code 40 reappears, it’s best to contact an experienced technician.

Honeywell Error Code e43

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

How to Fix Honeywell Thermostat Error e43

Reboot the router by unplugging it and leaving it that way for about 30 seconds. The thermostat could also be disconnected if you have recently updated the password or the Wi-Fi’s SSID, which is the name you give it.

Honeywell Error Code e1

Thermostats employ sensors to detect the temperature outdoors and indoors. If a sensor fails, you could see error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Honeywell Error Code 11n

Error code 11n could appear if the thermostat is unable to detect a heating or cooling unit. This might mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This can happen when the wiring is damaged or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to determine if there’s a poor electrical connection. When the wiring on your specific HVAC equipment is bad, the technician can replace it. If the thermostat itself is the source of the error code, it should probably be replaced.

Honeywell Error Code e2

If you notice error code e2 appear on your Honeywell smart thermostat, it can mean a few different things. For example, one of the sensors responsible for detecting the temperature isn’t operating properly. Other times, it means the router was disconnected from its power source before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code stems from sensor failure, a technician can troubleshoot and swap out the damaged sensor. When the problem originates from disconnected power, all you have to do is verify the router remains on throughout the setup process.