A Honeywell smart thermostat is a great way to optimize how you use your home comfort system. But like any utility, you could sometimes run across a problem. With its digital display, Honeywell smart thermostats can show an error code that certified technicians can use to understand what's wrong. Here are some of the most common error codes you could see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can encounter this error code when your home’s Wi-Fi connection did not present an IP address for the thermostat to hook up to. This can happen if your router does not execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the needed IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by verifying that your router has enabled DHCP. When it does, you might also need to power cycle the router and repeat the initial setup process with the thermostat. Completing this task should see to it that the DHCP is transmitted and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 appears when the password for connecting to your home’s Wi-Fi router is not correct. Once this error code has appeared 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 have to do to resolve error e02 is verify you’re putting in the correct Wi-Fi password when configuring 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 can also appear if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can render this error code. Finally, you might experience 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 check the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you turn the thermostat off and on again and error code 40 reappears, you should try 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 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

Reset the router by unplugging it and leaving it that way for about 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 provide it.

Error Code e1 for Honeywell Thermostats

Thermostats utilize sensors to detect 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 qualified technician can change out the sensor and reboot the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n may appear if the thermostat is unable to detect a heating or cooling unit. This might mean that the equipment itself is defective and unable to communicate with the thermostat. This can happen when the wiring is bad or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to determine if there’s a bad 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 issue, it will likely have to be replaced.

Honeywell Error Code e2

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it might mean a couple of different things. For example, one of the sensors responsible for detecting the temperature isn’t working correctly. In other cases, it means the router was disconnected from the outlet 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 damaged sensor. Any time the problem originates from disconnected power, all you’ll have to do is verify the router remains on during the setup process.