A Honeywell smart thermostat is an excellent way to optimize how you use your home comfort system. But like any mechanical system, you might sometimes experience a problem. With a digital display, Honeywell smart thermostats can display an error code that professional technicians use to understand what's wrong. Here are some of the most likely error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can encounter this error code if your home’s Wi-Fi connection did not present an IP address for the thermostat to hook up to. This can happen if the router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically supplies the necessary 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. When it does, you may also need to power cycle the router and repeat the initial setup process with the thermostat. Completing this task should ensure the DHCP is delivered and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for accessing 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 need to do to solve error e02 is ensure 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 alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this happens if the compressor isn’t working despite being directed to. But this error code could also show up if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. Lastly, you might see error code 40 if there’s an issue with the refrigerant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can examine 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 get a hold of an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat shows 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 your wide area network (WAN).

How to Fix Honeywell Thermostat Error e43

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

Honeywell Thermostat Error e1

Thermostats utilize sensors to determine the temperature outdoors and indoors. If a sensor breaks down, you might notice error code e1 appear 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 could appear when the thermostat can’t recognize a heating or cooling unit. This may mean that the equipment itself is faulty and unable to connect with the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can use a voltmeter to determine if there’s a poor electrical connection. If the wiring on your specific HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you’ve noticed error code e2 show up on your Honeywell smart thermostat, it might mean several different things. For example, one of the sensors that detects the temperature isn’t operating correctly. In other cases, 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 can troubleshoot and switch out the damaged sensor. If the problem comes from disconnected power, all you'll need to do is see to it that the router remains on during the setup process.