A Honeywell smart thermostat is an excellent way to fine-tune how you use your heating and cooling. But like any technology, you may occasionally run into a problem. With a digital display, Honeywell smart thermostats can display an error code that certified technicians use to get a better sense of what's going on. Here are several of the most common error codes you could see on your Honeywell smart thermostat.

Honeywell Error Code e42

You can receive this error code when your home’s Wi-Fi internet did not supply an IP address for the thermostat to connect with. This can take place if a router does not complete the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the required IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by verifying that your router can complete the DHCP. If it does, you usually also have to power cycle the router and perform the setup process again with your thermostat. This should see to it that the DHCP is delivered and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 is displayed whenever the password for accessing your home’s Wi-Fi router is incorrect. Once 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'll need to do to solve error e02 is make sure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most often, this happens once the compressor isn’t working despite being instructed to. But this error code can also show up if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, induced by poor airflow, can display this error code. Finally, you might experience 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 examine 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 in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If the Honeywell thermostat displays error code e43, it is failing to communicate with the router, and by extension your Wi-Fi. This might 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

Restart the router by unplugging it and leaving it that way for about 30 seconds. The thermostat may also be disconnected if you’ve recently updated the password or the Wi-Fi’s SSID, which is the name you create for it.

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to identify 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 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 failing to detect a heating or cooling unit. This might mean that the equipment itself is defective and unable to connect with 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 professional technician can employ a voltmeter to assess if there’s a poor electrical connection. If the wiring on your type of HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the source of the error code, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t functioning correctly. In other instances, it means the router was disconnected from power before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code stems from sensor failure, a technician should troubleshoot and replace the impacted sensor. If the problem stems from disconnected power, all you have to do is make sure the router stays on over the course of the setup process.