A Honeywell smart thermostat is a great way to better manage how you use your heating and cooling. But like any mechanical system, you could sometimes experience a problem. With a digital display, Honeywell smart thermostats can show an error code that certified technicians use to get a better sense of what's wrong. Here are several of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Error Code e42

You might receive this error code if your home’s Wi-Fi connection did not present an IP address for the thermostat to connect with. This can take place if your router doesn't complete the Dynamic Host Configuration Protocol, or DHCP. This process 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. Assuming it does, you may also have to power cycle the router and complete the initial setup process again with the thermostat. This should see to it that the DHCP is transmitted and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 appears whenever the password for connecting to your home’s Wi-Fi router was 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 try the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear error e02 is verify you’re putting in the correct Wi-Fi password when setting up the thermostat.

Honeywell Error Code 40

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. Most commonly, this happens if the compressor isn’t working despite being instructed to. But this error code may also surface if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. Lastly, you might experience error code 40 if there’s an issue with the refrigerant, 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 reset the thermostat and error code 40 reappears, it's time to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If your Honeywell thermostat displays error code e43, it is unable to 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 the 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 may also be disconnected if you have recently switched the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Error Code e1

Thermostats utilize sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you may notice error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can replace the sensor and restart the thermostat, which should take care of error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear if the thermostat is unable to detect a heating or cooling unit. This might mean that the equipment itself is faulty and unable to maintain a connection to the thermostat. This can happen when the wiring is damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to assess if there’s a faulty electrical connection. When the wiring on your type of HVAC equipment is bad, the technician can replace it. If the thermostat itself is the source of the error code, it should probably be replaced.

Honeywell Thermostat Error e2

If you see error code e2 show up on your Honeywell smart thermostat, it might mean a couple of different things. Sometimes, one of the sensors that detects the temperature isn’t functioning like it should. In other instances, it means the router was disconnected from power before the thermostat could complete 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 switch out the damaged sensor. Any time the problem stems from disconnected power, all you’ll have to do is verify the router remains on throughout the setup process.