Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any technology, you might occasionally run into a problem. With the 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 common error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can receive this error code when your home’s Wi-Fi connection did not provide an IP address for the thermostat to hook up to. This can occur if the router fails to perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically sends out the necessary IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by making sure that your router has enabled DHCP. When it does, you may also have to power cycle the router and perform the setup process again with your thermostat. Doing so should ensure the DHCP is transmitted and connects to the smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 appears whenever the password for communicating with your home’s Wi-Fi router was incorrect. After this error code is displayed for 30 seconds, the thermostat’s digital display will automatically progress to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

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

Honeywell Thermostat Error 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 appears when the compressor isn’t running despite being directed to. But this error code could also appear if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. Lastly, you might see error code 40 if there’s an issue with the coolant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can inspect 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 a hold of an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat displays error code e43, it can’t communicate with the router, and by extension the 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

Restart the router by unplugging it and leaving it that way for a short period. The thermostat may also be disconnected if you have recently switched the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

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

Honeywell Thermostat Error 11n

Error code 11n could appear if the thermostat can’t connect to a heating or cooling unit. This may mean that the equipment itself is defective and unable to communicate with the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can use a voltmeter to assess if there’s a faulty electrical connection. When the wiring on your type of HVAC equipment is bad, the technician can replace it. If the thermostat itself is the problem, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 pop up on your Honeywell smart thermostat, it might mean several different things. In some cases, one of the sensors used to detect the temperature isn’t operating properly. In other instances, it means the router was disconnected from power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code stems from sensor failure, a technician should troubleshoot and replace the impacted sensor. If the problem stems from disconnected power, all you’ll have to do is verify the router stays on throughout the setup process.