A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any utility, you may occasionally experience a problem. With a digital display, Honeywell smart thermostats can display an error code that certified technicians will use to figure out what's wrong. Here are some of the most common error codes you could see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You might encounter this error code when your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect to. This can happen if the router does not execute the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by making sure that your router can complete the DHCP. If it does, you might also have to power cycle the router and complete the initial setup process again with the thermostat. This should see to it that the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 occurs whenever the password for connecting to your home’s Wi-Fi router is incorrect. Once 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 solve error e02 is ensure you’re entering the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. For the most part, this appears once the compressor isn’t working despite being directed to. But this error code may also surface if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by blocked airflow, can lead to this error code. Finally, you might see error code 40 if there’s something wrong with the refrigerant, 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 best to contact an experienced technician.

Honeywell Error Code e43

If your Honeywell thermostat displays error code e43, it can’t communicate with the router, and by extension the Wi-Fi. This might 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

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

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

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

Error Code 11n for Honeywell Thermostats

Error code 11n may appear in situations where the thermostat can’t detect a heating or cooling unit. This may 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 is faulty.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can employ a voltmeter to find out if there’s a bad electrical connection. In situations where the wiring on your type of HVAC system is bad, the technician can replace it. When 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 might mean several different things. In some cases, one of the sensors that detects the temperature isn’t operating like it should. In other cases, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code is a result of sensor failure, a technician will troubleshoot and replace the impacted sensor. Any time the problem stems from disconnected power, all you’ll have to do is make sure the router stays on over the course of the setup process.