A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any technology, you may sometimes experience a problem. With its digital display, Honeywell smart thermostats can display an error code that trained technicians will use to understand what's going on. Here are several of the most known error codes you might see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may see this error code when your home’s Wi-Fi internet did not provide an IP address for the thermostat to connect with. This can occur if the router does not 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 clear error code e42 by making sure that your router can complete the DHCP. When it does, you might also need to power cycle the router and complete the initial setup process again with the thermostat. Completing this task should ensure the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed whenever the password for communicating with your home’s Wi-Fi router is not correct. After this error code has appeared for 30 seconds, the thermostat’s digital display will automatically progress 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 make sure you’re putting in 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 detected a malfunction. Most commonly, this appears once the compressor isn’t turning on despite being directed to. But this error code could also show up if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, caused by obstructed airflow, can display this error code. Finally, you might see 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 ordinary operation. If you restart the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Honeywell Error Code e43

If a Honeywell thermostat displays error code e43, it is unable to communicate with the router, and by extension your Wi-Fi. This might 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 could also be disconnected if you have recently switched the password or the Wi-Fi’s SSID, which is the name you give it.

Honeywell Error Code e1

Thermostats employ sensors to determine the temperature outdoors and indoors. If a sensor breaks down, you may notice error code e1 show up 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 clear error code e1.

Honeywell Error Code 11n

Error code 11n may appear if the thermostat can’t recognize 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 qualified technician can use a voltmeter to find out if there’s a bad electrical connection. If the wiring on your specific HVAC system is bad, the technician can replace it. If 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 see error code e2 show up on your Honeywell smart thermostat, it could 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 power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code stems from sensor failure, a technician will troubleshoot and switch out the affected sensor. If the problem stems from disconnected power, all you’ll have to do is see to it that the router stays on throughout the setup process.