A Honeywell smart thermostat is a great way to optimize how you use your home comfort system. But like any technology, you could sometimes run across a problem. With the digital display, Honeywell smart thermostats can show an error code that professional technicians will use to figure out what's going on. Here are some of the most likely 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 execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically transmits the needed IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by verifying that your router is enabled for DHCP. If it does, you may also need to power cycle the router and complete the initial setup process again with your thermostat. This should ensure the DHCP is delivered and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 is displayed if 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 automatically transitions to the Wi-Fi setup screen so you can try to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to clear error e02 is make sure you’re putting in the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can appear when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has identified a malfunction. For the most part, this appears when the compressor isn’t working despite being directed to. But this error code can also show up if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, induced by obstructed airflow, can lead to this error code. And finally, you might encounter error code 40 if there’s something wrong with the refrigerant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular operation. If you turn the thermostat off and on again and error code 40 reappears, you should try to contact an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat shows error code e43, it is unable to communicate with the router, and by extension the Wi-Fi. This might 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 around 30 seconds. The thermostat might also be disconnected if you have recently updated the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you could 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.

Error Code 11n for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error 11n

A licensed technician can use a voltmeter to determine if there’s a faulty electrical connection. When the wiring on your specific HVAC equipment is bad, the technician can replace it. When 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 could mean a few different things. In some cases, one of the sensors used to detect the temperature isn’t operating 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 swap out the impacted sensor. If the problem stems from disconnected power, all you’ll have to do is verify the router remains on over the course of the setup process.