A Honeywell smart thermostat is a great way to optimize how you use your heating and cooling. But like any utility, you might occasionally run into a problem. With a digital display, Honeywell smart thermostats can show an error code that certified technicians can use to figure out what's going on. Here are some of the most known error codes you could see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may receive this error code in the event that your home’s Wi-Fi connection did not present an IP address for the thermostat to connect to. This can take place if the router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically sends out the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by verifying that your router has enabled DHCP. When it does, you usually also need to power cycle the router and complete the initial setup process again with the thermostat. Doing so should ensure the DHCP is sent and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed if the password for accessing your home’s Wi-Fi router was incorrect. After this error code has appeared 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 have to do to solve error e02 is ensure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can appear when the thermostat is notified that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this occurs when the compressor isn’t turning on despite being instructed to. But this error code can also appear if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by poor airflow, can render this error code. Finally, you might encounter error code 40 if there’s a problem 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 normal operation. If you restart 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 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

Reboot the router by unplugging it and leaving it that way for a short period. The thermostat could also be disconnected if you have recently changed the password or the Wi-Fi’s SSID, which is the name you give it.

Honeywell Thermostat Error e1

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

How to Fix Honeywell Thermostat Error e1

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

Honeywell Error Code 11n

Error code 11n may appear if the thermostat is unable to recognize 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 defective or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can utilize a voltmeter to find out if there’s a poor 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 problem, it will likely have to be replaced.

Honeywell Error Code e2

If you see error code e2 pop up on your Honeywell smart thermostat, it can mean a couple of different things. Sometimes, one of the sensors that detects the temperature isn’t functioning like it should. 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

In situations where the error code is a result of sensor failure, a technician should troubleshoot and switch out the damaged sensor. Any time the problem originates from disconnected power, all you’ll have to do is see to it that the router remains on throughout the setup process.