A Honeywell smart thermostat is an excellent way to fine-tune how you use your home comfort system. But like any utility, you could occasionally experience a problem. With the digital display, Honeywell smart thermostats can provide an error code that professional technicians will use to understand what's going on. Here are several of the most likely error codes you might see on your Honeywell smart thermostat.

Honeywell Error Code e42

You may encounter this error code when your home’s Wi-Fi internet did not supply an IP address for the thermostat to hook up to. This can take place if a router does not perform 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 clear error code e42 by making sure that your router is enabled for DHCP. Assuming it does, you may also have to power cycle the router and complete the initial setup process again with the thermostat. Completing this task should see to it that the DHCP is transmitted and connects to the smart thermostat.

Honeywell Thermostat Error e02

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

How to Fix Honeywell Thermostat Error e02

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

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most commonly, this appears once the compressor isn’t running despite being instructed to. But this error code can also show up if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, triggered by poor airflow, can lead to 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 normal operation. If you reset the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Honeywell Thermostat Error e43

If your Honeywell thermostat presents error code e43, it can’t communicate with the router, and by extension the 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 might also be disconnected if you recently updated the password or the Wi-Fi’s SSID, which is the name you give it.

Error Code e1 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e1

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

Honeywell Error Code 11n

Error code 11n could appear when the thermostat can’t connect to a heating or cooling unit. This might mean that the equipment itself is defective and unable to connect with 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 professional technician can utilize a voltmeter to determine if there’s a poor electrical connection. If the wiring on your existing HVAC system is bad, the technician can replace it. When the thermostat itself is the source of the error code, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 show up on your Honeywell smart thermostat, it could mean several different things. For example, one of the sensors that detects the temperature isn’t operating correctly. In other cases, it means the router was disconnected from power before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code stems from sensor failure, a technician should troubleshoot and swap out the affected sensor. If the problem stems from disconnected power, all you’ll have to do is make sure the router stays on during the setup process.