Error Code E42: How to Fix This Honeywell Thermostat Code

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

Honeywell Error Code e42

You might encounter this error code if your home’s Wi-Fi internet did not present 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 process automatically sends out the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by verifying that your router has enabled DHCP. When it does, you might also need to power cycle the router and complete the initial setup process again with your thermostat. Completing this task should see to it that the DHCP is delivered and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed if the password for connecting to your home’s Wi-Fi router was incorrect. When this error code appears for 30 seconds, the thermostat’s digital display automatically transitions 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 solve error e02 is ensure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can appear when the thermostat is informed 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 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. Finally, you might see error code 40 if there’s something wrong with the coolant, 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, it's time to get in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If the Honeywell thermostat presents 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

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

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor fails, you might notice error code e1 turn 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.

Error Code 11n for Honeywell Thermostats

Error code 11n may appear when the thermostat can’t connect to a heating or cooling unit. This may mean that the equipment itself is defective and unable to maintain a connection to 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 licensed technician can employ a voltmeter to assess if there’s a poor electrical connection. In situations where the wiring on your specific HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 show up on your Honeywell smart thermostat, it could mean several different things. In some cases, one of the sensors used to detect the temperature isn’t working properly. Other times, it means the router was disconnected from the outlet before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code stems from sensor failure, a technician can troubleshoot and replace the affected sensor. Any time the problem comes from disconnected power, all you'll need to do is verify the router stays on throughout the setup process.