A Honeywell smart thermostat is a great way to optimize how you use your home comfort system. But like any utility, you could sometimes experience a problem. With its digital display, Honeywell smart thermostats can show an error code that professional technicians can use to figure out what's going on. Here are several of the most common error codes you might see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may see this error code in the event that your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect to. This can occur if your router fails to complete the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically transmits the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router can complete the DHCP. If it does, you may also have to power cycle the router and complete the initial setup process again with the thermostat. Completing this task should ensure the DHCP is delivered and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 occurs when the password for communicating with your home’s Wi-Fi router is not correct. After this error code has appeared 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 need to do to resolve error e02 is ensure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can show up when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this occurs if the compressor isn’t turning on despite being instructed to. But this error code may also surface if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, induced by blocked airflow, can display this error code. And finally, you could see error code 40 if there’s something wrong with the coolant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can check 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 time to get in touch with 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 the 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

Reboot the router by unplugging it and leaving it that way for a short period. The thermostat could 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 utilize sensors to detect the temperature outdoors and indoors. If a sensor malfunctions, you could see error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A qualified technician can replace the sensor and reboot the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is failing to recognize a heating or cooling unit. This might mean that the equipment itself is defective and unable to connect with the thermostat. This sometimes happens when the wiring is bad or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can use a voltmeter to assess if there’s a poor electrical connection. In situations where the wiring on your existing HVAC equipment is bad, the technician can replace it. In situations where the thermostat itself is the source of the error code, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 show up on your Honeywell smart thermostat, it might mean a couple of different things. For example, one of the sensors used to detect the temperature isn’t functioning properly. Other times, it means the router was disconnected from its power source before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is caused by sensor failure, a technician will troubleshoot and replace the affected sensor. Any time the problem stems from disconnected power, all you have to do is verify the router remains on throughout the setup process.