A Honeywell smart thermostat is an excellent way to better manage how you use your HVAC system. But like any mechanical system, you could occasionally run into a problem. With its digital display, Honeywell smart thermostats can show an error code that certified technicians can use to understand what's happening. Here are some of the most common error codes you could see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may see this error code if your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect to. This can occur if the router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically sends out the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router can complete the DHCP. When it does, you might also need to power cycle the router and perform the setup process again with your thermostat. This should ensure the DHCP is delivered and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears when the password for communicating with your home’s Wi-Fi router is incorrect. After this error code has appeared for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

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

Honeywell Error Code 40

Error code 40 can appear when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this appears when the compressor isn’t turning on despite being instructed to. But this error code can also show up 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. Lastly, you may see 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 inspect 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 time to contact an experienced technician.

Error Code e43 for Honeywell Thermostats

If your Honeywell thermostat presents error code e43, it is unable to communicate with the router, and by extension the 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’ve recently updated the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Error Code e1

Thermostats utilize sensors to detect the temperature outdoors and indoors. If a sensor breaks down, you may see error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Honeywell Thermostat Error 11n

Error code 11n could appear if the thermostat is failing to connect to a heating or cooling unit. This can mean that the equipment itself is defective and unable to communicate with the thermostat. This sometimes happens when the wiring is defective 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 faulty electrical connection. In situations where the wiring on your specific HVAC equipment is bad, the technician can replace it. When the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 appear on your Honeywell smart thermostat, it can mean several different things. For example, 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 finished the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician should troubleshoot and swap out the damaged sensor. When the problem stems from disconnected power, all you have to do is see to it that the router stays on during the setup process.