A Honeywell smart thermostat is an easy way to optimize how you use your HVAC system. But like any technology, you could occasionally experience a problem. With the digital display, Honeywell smart thermostats can display an error code that trained technicians will use to understand what's happening. Here are a few of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can encounter this error code if your home’s Wi-Fi internet did not supply an IP address for the thermostat to hook up to. This can take place if the router fails to complete the Dynamic Host Configuration Protocol, or DHCP. This procedure 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 making sure that your router can complete the DHCP. Assuming it does, you may 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 your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 is displayed whenever the password for communicating with your home’s Wi-Fi router was incorrect. Once 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 try the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to solve error e02 is ensure you’re entering the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 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 appears once the compressor isn’t working despite being directed to. But this error code could also show up if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by poor airflow, can lead to this error code. Lastly, you might encounter 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 regular operation. If you restart the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Honeywell Error Code e43

If your Honeywell thermostat displays error code e43, it is failing to communicate with the router, and by extension your 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

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

Error Code e1 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e1

A skilled technician can replace the sensor and restart the thermostat, which should clear error code e1.

Honeywell Error Code 11n

Error code 11n may appear if the thermostat is unable to recognize a heating or cooling unit. This may mean that the equipment itself is defective and unable to communicate with the thermostat. This can happen when the wiring is defective or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to determine if there’s a poor electrical connection. If the wiring on your type of HVAC system is bad, the technician can replace it. When the thermostat itself is the issue, 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 could mean a few different things. Sometimes, one of the sensors used to detect the temperature isn’t working correctly. In other cases, it means the router was disconnected from its power source before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is a result of sensor failure, a technician will troubleshoot and switch out the damaged sensor. Any time the problem comes from disconnected power, all you have to do is make sure the router remains on over the course of the setup process.