A Honeywell smart thermostat is a great way to better manage how you use your HVAC system. But like any technology, you could occasionally run across a problem. With a digital display, Honeywell smart thermostats can display an error code that certified technicians will use to understand what's going on. Here are several of the most common error codes you may see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You can encounter this error code in the event that your home’s Wi-Fi connection did not present an IP address for the thermostat to hook up to. This can occur if your router fails to perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the required IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router has enabled DHCP. When it does, you might also need to power cycle the router and repeat the initial setup process with the thermostat. This should see to it that the DHCP is sent and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 appears if the password for connecting to your home’s Wi-Fi router was incorrect. Once this error code is displayed for 30 seconds, the thermostat’s digital display should automatically transition 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 typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can appear when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most often, this happens if the compressor isn’t working despite being instructed to. But this error code may also appear if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, induced by poor airflow, can display this error code. And finally, you could 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 check 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, you should try to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If the Honeywell thermostat displays error code e43, it is failing to communicate with the router, and by extension the Wi-Fi. This can 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 a short period. The thermostat could also be disconnected if you recently updated the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

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

Honeywell Error Code 11n

Error code 11n could appear when the thermostat can’t recognize a heating or cooling unit. This might mean that the equipment itself is faulty and unable to communicate with the thermostat. This can happen when the wiring is damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can use a voltmeter to find out if there’s a poor electrical connection. When the wiring on your existing HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 pop up on your Honeywell smart thermostat, it could mean a few different things. In some cases, one of the sensors that detects the temperature isn’t functioning properly. In other cases, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code stems from sensor failure, a technician will troubleshoot and replace the damaged sensor. When the problem stems from disconnected power, all you’ll have to do is see to it that the router stays on over the course of the setup process.