A Honeywell smart thermostat is an excellent way to fine-tune how you use your heating and cooling. But like any utility, you might sometimes run into a problem. With the digital display, Honeywell smart thermostats can show an error code that certified technicians will use to get a better sense of what's happening. Here are a few of the most known error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may see this error code when your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect to. This can take place if a router doesn't perform 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 is enabled for DHCP. When it does, you usually also need to power cycle the router and repeat the initial setup process with your thermostat. This should see to it that the DHCP is transmitted and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 is displayed if the password for accessing your home’s Wi-Fi router is not correct. 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 to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to resolve error e02 is make sure you’re entering the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most often, this appears when the compressor isn’t working despite being directed to. But this error code may also appear if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by poor airflow, can render this error code. Lastly, you might experience error code 40 if there’s a problem 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 ordinary operation. If you restart the thermostat and error code 40 reappears, you should try to contact an experienced technician.

Honeywell Error Code e43

If your Honeywell thermostat shows error code e43, it is failing to communicate with the router, and by extension the Wi-Fi. This might happen if the router’s ethernet cable isn’t plugged in or it isn’t communicating with the wide area network (WAN).

How to Fix Honeywell Thermostat Error e43

Restart 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 provide it.

Error Code e1 for Honeywell Thermostats

Thermostats use sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you could see error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can swap out the sensor and reset the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n may appear if the thermostat can’t connect to a heating or cooling unit. This can mean that the equipment itself is faulty and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

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

Error Code e2 for Honeywell Thermostats

If you notice error code e2 pop up on your Honeywell smart thermostat, it could mean several different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t working correctly. 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 is caused by sensor failure, a technician can troubleshoot and replace the damaged sensor. Any time the problem originates from disconnected power, all you'll need to do is verify the router remains on over the course of the setup process.