A Honeywell smart thermostat is a great way to better manage how you use your home comfort system. But like any utility, you may sometimes run across a problem. With its digital display, Honeywell smart thermostats can display an error code that certified technicians will use to figure out what's happening. Here are some of the most likely error codes you could 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 connection did not provide an IP address for the thermostat to hook up to. This can occur if a router does not complete the Dynamic Host Configuration Protocol, or DHCP. This process automatically supplies the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by making sure that your router has enabled 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 see to it that the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 occurs whenever the password for connecting to your home’s Wi-Fi router is incorrect. After this error code appears 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 clear error e02 is ensure you’re typing the correct Wi-Fi password when setting up the thermostat.

Honeywell Error Code 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. For the most part, this occurs once the compressor isn’t working despite being directed to. But this error code may also surface if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by poor airflow, can render this error code. Lastly, you may experience 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 examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you restart the thermostat and error code 40 reappears, you should try to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If a Honeywell thermostat shows error code e43, it is failing to communicate with the router, and by extension your Wi-Fi. This may 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 recently switched 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 detect the temperature outdoors and indoors. If a sensor fails, you might notice error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can change out the sensor and reboot the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n may appear when the thermostat is failing to recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to communicate with the thermostat. This can happen when the wiring is bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can use a voltmeter to determine if there’s a faulty electrical connection. When the wiring on your type of HVAC equipment is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Error Code e2

If you’ve noticed error code e2 pop up on your Honeywell smart thermostat, it could mean several different things. In some cases, one of the sensors that detects the temperature isn’t functioning like it should. In other cases, it means the router was disconnected from its power source before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is a result of sensor failure, a technician will troubleshoot and replace the damaged sensor. Any time the problem originates from disconnected power, all you have to do is verify the router remains on over the course of the setup process.