Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is an excellent way to optimize how you use your heating and cooling. But like any mechanical system, you could occasionally run into a problem. With a digital display, Honeywell smart thermostats can show an error code that trained technicians can use to understand what's wrong. Here are some of the most likely error codes you could see on your Honeywell smart thermostat.

Honeywell Error Code e42

You may encounter this error code in the event that your home’s Wi-Fi internet did not provide an IP address for the thermostat to connect to. This can occur if the router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically supplies the required IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by confirming that your router can complete the DHCP. If it does, you might also need to power cycle the router and complete the initial setup process again with your thermostat. Doing so should see to it that the DHCP is sent and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for connecting to your home’s Wi-Fi router is not correct. When this error code appears 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 have to do to clear 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 pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this happens if the compressor isn’t running despite being directed to. But this error code could 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 display this error code. And finally, you may see 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 examine 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 in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If your Honeywell thermostat presents error code e43, it is failing 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

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

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to determine the temperature outdoors and indoors. If a sensor fails, you could see error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Error Code 11n for Honeywell Thermostats

Error code 11n may appear in situations where the thermostat can’t connect to a heating or cooling unit. This may mean that the equipment itself is faulty and unable to connect with 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 licensed technician can employ a voltmeter to find out if there’s a faulty electrical connection. When the wiring on your specific HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the source of the error code, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. In some cases, one of the sensors used to detect the temperature isn’t functioning correctly. In other instances, it means the router was disconnected from its power source before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is caused by sensor failure, a technician will troubleshoot and switch out the impacted sensor. If the problem stems from disconnected power, all you have to do is make sure the router remains on over the course of the setup process.