A Honeywell smart thermostat is an excellent way to optimize how you use your heating and cooling. But like any utility, you may occasionally experience a problem. With its digital display, Honeywell smart thermostats can show an error code that certified 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 internet did not present an IP address for the thermostat to hook up to. This can happen if your router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies 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 has enabled DHCP. Assuming it does, you may also need to power cycle the router and perform the setup process again with your thermostat. Doing so should see to it that the DHCP is sent and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for accessing your home’s Wi-Fi router was incorrect. After 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 have to do to solve error e02 is verify you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can appear when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most commonly, this occurs if the compressor isn’t working despite being instructed to. But this error code could also appear if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by blocked airflow, can lead to this error code. And finally, you may experience 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 check the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you reset the thermostat and error code 40 reappears, you should try to contact an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat displays error code e43, it can’t 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

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

Honeywell Thermostat Error e1

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

How to Fix Honeywell Thermostat Error e1

A qualified technician can swap out the sensor and reboot the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

Error code 11n may appear when the thermostat is failing to connect to 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 bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can utilize a voltmeter to find out if there’s a bad electrical connection. If the wiring on your specific 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’ve noticed error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. For example, one of the sensors responsible for detecting the temperature isn’t operating like it should. In other instances, 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 stems from sensor failure, a technician will troubleshoot and switch out the impacted sensor. Any time the problem originates from disconnected power, all you’ll have to do is see to it that the router remains on throughout the setup process.