A Honeywell smart thermostat is a great way to fine-tune how you use your heating and cooling. But like any mechanical system, you may sometimes run into a problem. With the digital display, Honeywell smart thermostats can display an error code that trained technicians can use to understand what's going on. Here are some of the most common error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can receive this error code if 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 required IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router has enabled DHCP. Assuming it does, you usually also have to power cycle the router and repeat the initial setup process with the thermostat. Doing so should ensure the DHCP is transmitted and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for accessing your home’s Wi-Fi router was incorrect. After this error code appears for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear error e02 is make sure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can pop up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most commonly, this appears when the compressor isn’t turning on despite being directed to. But this error code may also appear if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can lead to this error code. Finally, you might encounter error code 40 if there’s an issue with the coolant, 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 turn the thermostat off and on again and error code 40 reappears, it’s best 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 the 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

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 give it.

Error Code e1 for Honeywell Thermostats

Thermostats use sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you could see error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A qualified technician can replace the sensor and reset the thermostat, which should resolve error code e1.

Honeywell Error Code 11n

Error code 11n can appear in situations where the thermostat is failing to recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is bad 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 poor electrical connection. If the wiring on your specific HVAC equipment is bad, the technician can replace it. When the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 appear on your Honeywell smart thermostat, it might mean several different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t working properly. In other cases, 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 stems from sensor failure, a technician should troubleshoot and swap out the impacted sensor. When the problem stems from disconnected power, all you'll need to do is make sure the router remains on throughout the setup process.