A Honeywell smart thermostat is an easy way to optimize how you use your HVAC system. But like any utility, you may sometimes run into a problem. With its digital display, Honeywell smart thermostats can provide an error code that professional technicians will use to get a better sense of what's happening. Here are some of the most common error codes you could see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You might receive this error code if your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect with. This can occur if your router doesn't perform 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 verifying that your router is enabled for DHCP. Assuming it does, you usually also need to power cycle the router and perform the setup process again with your thermostat. Completing this task should see to it that the DHCP is transmitted and connects to the smart thermostat.

Honeywell Thermostat Error e02

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

How to Fix Honeywell Thermostat Error e02

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

Honeywell Thermostat Error 40

Error code 40 can show up when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most often, this occurs when the compressor isn’t running despite being directed to. But this error code can also surface if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, induced by obstructed airflow, can display this error code. Finally, you might experience error code 40 if there’s an issue 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 restart the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat shows error code e43, it can’t 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 the 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 might also be disconnected if you have recently updated 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 identify the temperature outdoors and indoors. If a sensor malfunctions, you might notice error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can replace the sensor and reset the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is failing to detect a heating or cooling unit. This may mean that the equipment itself is faulty and unable to communicate 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 find out if there’s a poor electrical connection. If the wiring on your existing HVAC equipment is bad, the technician can replace it. When the thermostat itself is the problem, it should probably be replaced.

Honeywell Error Code e2

If you see error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. Sometimes, one of the sensors used to detect the temperature isn’t working correctly. In other instances, it means the router was disconnected from the outlet before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code stems from sensor failure, a technician should troubleshoot and swap out the damaged sensor. Any time the problem stems from disconnected power, all you'll need to do is see to it that the router remains on over the course of the setup process.