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

Honeywell Thermostat Error e42

You may see this error code when your home’s Wi-Fi internet did not provide an IP address for the thermostat to connect with. This can happen if a router fails to complete the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by verifying that your router has enabled DHCP. Assuming it does, you usually also have to power cycle the router and perform the setup process again with the thermostat. Completing this task should ensure the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed when the password for accessing your home’s Wi-Fi router was incorrect. Once this error code appears 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 ensure you’re entering the correct Wi-Fi password when configuring 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 detected a malfunction. For the most part, this occurs once the compressor isn’t working despite being directed to. But this error code may also show up if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. Lastly, you may encounter 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 regular operation. If you restart the thermostat and error code 40 reappears, it's time 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 your 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

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

Honeywell Thermostat Error e1

Thermostats use sensors to identify the temperature outdoors and indoors. If a sensor malfunctions, you might notice error code e1 turn 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 Error Code 11n

Error code 11n may appear when the thermostat is failing to connect to a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to connect with the thermostat. This sometimes happens when the wiring is bad or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can use a voltmeter to determine if there’s a faulty electrical connection. In situations where the wiring on your type of HVAC system is bad, the technician can replace it. When the thermostat itself is the problem, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you see error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. In some cases, one of the sensors used to detect the temperature isn’t operating like it should. In other instances, it means the router was disconnected from power before the thermostat finished 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 replace the affected sensor. Any time the problem stems from disconnected power, all you’ll have to do is verify the router remains on over the course of the setup process.