A Honeywell smart thermostat is an easy way to optimize how you use your heating and cooling. But like any mechanical system, you might occasionally experience a problem. With the digital display, Honeywell smart thermostats can display an error code that certified technicians will use to figure out what's wrong. Here are several of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You might receive this error code if your home’s Wi-Fi internet did not supply an IP address for the thermostat to connect with. This can occur if a router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically transmits the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by making sure that your router can complete the DHCP. If it does, you usually also have to power cycle the router and complete the initial setup process again with your thermostat. Doing so should see to it that the DHCP is delivered and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears if the password for communicating with your home’s Wi-Fi router is incorrect. Once this error code has appeared for 30 seconds, the thermostat’s digital display will automatically progress to the Wi-Fi setup screen so you can try to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to clear error e02 is ensure you’re putting in the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most often, this appears if the compressor isn’t running despite being directed to. But this error code can also surface if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can display this error code. Lastly, you might encounter 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 ordinary operation. If you reset the thermostat and error code 40 reappears, you should try to get in touch with an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat shows error code e43, it is unable to communicate with the router, and by extension the Wi-Fi. This might 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

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

Honeywell Thermostat Error e1

Thermostats utilize sensors to detect the temperature outdoors and indoors. If a sensor malfunctions, you could notice error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A qualified technician can change out the sensor and reboot the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is unable to recognize a heating or cooling unit. This can 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 is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to determine if there’s a faulty electrical connection. If the wiring on your type of HVAC system is bad, the technician can replace it. If the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it can mean a few different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t operating correctly. In other instances, it means the router was disconnected from the outlet before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code is a result of sensor failure, a technician can troubleshoot and switch out the damaged sensor. If the problem originates from disconnected power, all you'll need to do is see to it that the router stays on over the course of the setup process.