A Honeywell smart thermostat is an excellent way to fine-tune how you use your heating and cooling. But like any utility, you might occasionally run into a problem. With its digital display, Honeywell smart thermostats can display an error code that trained technicians use to understand what's wrong. Here are some of the most common error codes you might see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You can receive this error code in the event that your home’s Wi-Fi internet did not supply an IP address for the thermostat to hook up to. This can happen if your router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router is enabled for DHCP. When it does, you may also have to power cycle the router and repeat the initial setup process with the thermostat. This should see to it that the DHCP is transmitted and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 occurs if the password for connecting to your home’s Wi-Fi router is incorrect. Once this error code appears for 30 seconds, the thermostat’s digital display will automatically progress to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to solve error e02 is ensure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can appear when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. For the most part, this appears if the compressor isn’t running despite being instructed to. But this error code could also surface 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 render this error code. Finally, you could 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 examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular operation. If you reset the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If your Honeywell thermostat shows error code e43, it is failing to communicate with the router, and by extension the 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 might also be disconnected if you’ve recently changed the password or the Wi-Fi’s SSID, which is the name you give it.

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to detect the temperature outdoors and indoors. If a sensor fails, you might notice error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A qualified technician can swap out the sensor and reset the thermostat, which should resolve error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear if the thermostat can’t connect to a heating or cooling unit. This may mean that the equipment itself is faulty and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is bad or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can use a voltmeter to find out if there’s a faulty electrical connection. When 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 see error code e2 show up on your Honeywell smart thermostat, it could mean a few different things. Sometimes, one of the sensors that detects the temperature isn’t functioning correctly. In other cases, it means the router was disconnected from its power source before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code is a result of sensor failure, a technician should troubleshoot and swap out the impacted sensor. When the problem originates from disconnected power, all you have to do is see to it that the router remains on over the course of the setup process.