A Honeywell smart thermostat is an easy way to optimize how you use your HVAC system. But like any technology, you might occasionally experience a problem. With the digital display, Honeywell smart thermostats can provide an error code that professional technicians can use to understand what's going on. Here are some 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 connection did not provide an IP address for the thermostat to hook up to. This can happen if a router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the necessary IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by making sure that your router has enabled DHCP. If it does, you might also need to power cycle the router and repeat the initial setup process with your thermostat. Doing so should see to it that the DHCP is delivered and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 appears if the password for connecting to your home’s Wi-Fi router is incorrect. When this error code is displayed for 30 seconds, the thermostat’s digital display will automatically progress 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 putting in the correct Wi-Fi password when configuring the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this occurs once the compressor isn’t running despite being directed to. But this error code can also surface if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by obstructed airflow, can display this error code. Lastly, you may see error code 40 if there’s a problem 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 ordinary operation. If you reset the thermostat and error code 40 reappears, it's time to contact an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat displays error code e43, it can’t communicate with the router, and by extension your Wi-Fi. This can 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 a short period. The thermostat might also be disconnected if you’ve recently changed the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Error Code e1

Thermostats use sensors to determine the temperature outdoors and indoors. If a sensor malfunctions, 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 restart the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is unable to connect to a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to maintain a connection to 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 qualified technician can utilize a voltmeter to assess if there’s a bad electrical connection. When the wiring on your specific HVAC equipment is bad, the technician can replace it. If the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it could mean a couple of different things. In some cases, one of the sensors that detects the temperature isn’t functioning correctly. In other instances, it means the router was disconnected from the outlet before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is a result of sensor failure, a technician will troubleshoot and switch out the affected sensor. When the problem originates from disconnected power, all you have to do is make sure the router remains on during the setup process.