Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is a great way to better manage how you use your heating and cooling. But like any mechanical system, you might sometimes run into a problem. With its digital display, Honeywell smart thermostats can provide an error code that trained technicians can use to get a better sense of what's wrong. Here are several of the most known error codes you might see on your Honeywell smart thermostat.

Honeywell Error Code e42

You might see this error code when your home’s Wi-Fi connection did not supply an IP address for the thermostat to hook up to. This can take place if the router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically transmits the needed IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by verifying that your router can complete the DHCP. If it does, you may also need to power cycle the router and perform the setup process again with the thermostat. This should ensure the DHCP is sent 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 is incorrect. When this error code is displayed 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 verify 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 alerted that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most often, this appears once the compressor isn’t turning on despite being instructed to. But this error code may also appear if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can lead to this error code. And finally, you may experience error code 40 if there’s a problem 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 regular operation. If you reset the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If a Honeywell thermostat presents error code e43, it is unable to 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 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 could also be disconnected if you’ve recently updated the password or the Wi-Fi’s SSID, which is the name you create for it.

Error Code e1 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e1

A qualified technician can replace the sensor and reset the thermostat, which should clear error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear when the thermostat can’t detect a heating or cooling unit. This can mean that the equipment itself is faulty and unable to maintain a connection to the thermostat. This can happen when the wiring is defective or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to assess if there’s a bad electrical connection. If the wiring on your existing HVAC equipment is bad, the technician can replace it. When the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Error Code e2

If you see error code e2 appear on your Honeywell smart thermostat, it might mean a couple of different things. In some cases, one of the sensors responsible for detecting the temperature isn’t functioning correctly. Other times, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is a result of sensor failure, a technician should troubleshoot and replace the affected sensor. Any time the problem originates from disconnected power, all you’ll have to do is verify the router stays on during the setup process.