A Honeywell smart thermostat is a great way to better manage how you use your heating and cooling. But like any technology, you might sometimes run into a problem. With the digital display, Honeywell smart thermostats can show an error code that trained technicians use to understand what's happening. Here are several of the most likely error codes you could see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may receive this error code when your home’s Wi-Fi internet did not provide an IP address for the thermostat to connect with. This can occur if the router doesn't complete the Dynamic Host Configuration Protocol, or DHCP. This process automatically supplies the needed IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by verifying 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 transmitted and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 occurs if the password for accessing your home’s Wi-Fi router is not correct. When this error code has appeared for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

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

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is notified 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 turning on despite being directed to. But this error code may also appear if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, triggered by poor airflow, can lead to this error code. Lastly, you could 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 normal operation. If you restart the thermostat and error code 40 reappears, it's time to get in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If your Honeywell thermostat displays error code e43, it is unable to communicate with the router, and by extension your Wi-Fi. This could 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 around 30 seconds. The thermostat might also be disconnected if you’ve recently switched the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats employ sensors to detect the temperature outdoors and indoors. If a sensor fails, you may see 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 reset the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

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

How to Fix Honeywell Thermostat Error 11n

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

Honeywell Thermostat Error e2

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

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician can troubleshoot and swap out the affected sensor. When the problem comes from disconnected power, all you'll need to do is see to it that the router stays on throughout the setup process.