A Honeywell smart thermostat is a great way to fine-tune how you use your HVAC system. But like any utility, you may sometimes run across a problem. With its digital display, Honeywell smart thermostats can show an error code that certified technicians can use to get a better sense of what's wrong. Here are several of the most common error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You might see this error code when your home’s Wi-Fi internet did not present an IP address for the thermostat to hook up to. This can take place if your router fails to perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router is enabled for DHCP. When it does, you usually also need to power cycle the router and perform the setup process again with your thermostat. Doing so should ensure the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed when the password for communicating with your home’s Wi-Fi router is not correct. Once this error code is displayed for 30 seconds, the thermostat’s digital display automatically transitions 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 resolve error e02 is make sure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this appears when the compressor isn’t working 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. And finally, you might 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 regular operation. If you reset the thermostat and error code 40 reappears, it's time to get in touch with an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat shows 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 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 recently switched the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats use sensors to identify the temperature outdoors and indoors. If a sensor fails, you might see error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can replace the sensor and reboot the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear when the thermostat can’t connect to a heating or cooling unit. This may mean that the equipment itself is faulty and unable to connect with the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can use a voltmeter to assess if there’s a bad electrical connection. If the wiring on your existing HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it can mean a couple of different things. For example, one of the sensors that detects the temperature isn’t operating correctly. Other times, it means the router was disconnected from its power source before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is caused by sensor failure, a technician will troubleshoot and swap out the affected sensor. When the problem stems from disconnected power, all you have to do is see to it that the router stays on over the course of the setup process.