A Honeywell smart thermostat is a great way to better manage how you use your HVAC system. But like any technology, you might sometimes run across a problem. With the 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 some of the most likely error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error 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 a router does not execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the necessary IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by confirming that your router is enabled for DHCP. If it does, you usually also need to power cycle the router and repeat the initial setup process with your thermostat. Completing this task should ensure the DHCP is delivered and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 appears when the password for communicating with your home’s Wi-Fi router is not correct. Once this error code appears for 30 seconds, the thermostat’s digital display will automatically progress to the Wi-Fi setup screen so you can try to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to clear error e02 is ensure you’re typing the correct Wi-Fi password when configuring 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 often, this happens once the compressor isn’t turning on despite being instructed to. But this error code can also appear if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by poor airflow, can lead to this error code. Lastly, you may see error code 40 if there’s an issue 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 ordinary operation. If you turn the thermostat off and on again and error code 40 reappears, it's time to contact an experienced technician.

Honeywell Error Code e43

If your Honeywell thermostat shows error code e43, it can’t communicate with the router, and by extension your Wi-Fi. This can 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 a short period. The thermostat could also be disconnected if you’ve recently changed the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor fails, you could 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 restart the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

Error code 11n could appear if the thermostat is failing to recognize a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can employ a voltmeter to determine if there’s a bad electrical connection. When the wiring on your existing HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 pop up on your Honeywell smart thermostat, it could mean several different things. Sometimes, one of the sensors used to detect the temperature isn’t functioning like it should. 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

In situations where the error code is a result of sensor failure, a technician should troubleshoot and replace the damaged sensor. If the problem originates from disconnected power, all you'll need to do is verify the router stays on throughout the setup process.