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

Error Code e42 for Honeywell Thermostats

You can encounter this error code if your home’s Wi-Fi internet did not supply an IP address for the thermostat to connect with. This can take place if your router fails to perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the necessary 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. When it does, you usually also need to power cycle the router and repeat the initial setup process with your thermostat. This should ensure the DHCP is transmitted and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 occurs if the password for communicating with your home’s Wi-Fi router was incorrect. Once this error code appears for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to clear error e02 is verify you’re typing the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can show up when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this occurs if the compressor isn’t working despite being instructed to. But this error code could also appear if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by poor airflow, can render this error code. Lastly, you may encounter error code 40 if there’s something wrong 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 turn the thermostat off and on again and error code 40 reappears, you should try to get in touch with 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 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

Reset the router by unplugging it and leaving it that way for around 30 seconds. The thermostat might also be disconnected if you 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 use 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 swap out the sensor and restart the thermostat, which should clear error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n may appear when the thermostat is unable to connect to a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to connect with the thermostat. This can happen when the wiring is bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to assess if there’s a poor electrical connection. In situations where the wiring on your type of HVAC system is bad, the technician can replace it. If the thermostat itself is the problem, it should probably be replaced.

Honeywell Error Code e2

If you see error code e2 show up on your Honeywell smart thermostat, it can mean a few different things. For example, one of the sensors responsible for detecting the temperature isn’t operating like it should. In other cases, it means the router was disconnected from the outlet 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 replace the damaged sensor. Any time the problem originates from disconnected power, all you'll need to do is verify the router remains on during the setup process.