A Honeywell smart thermostat is an excellent way to optimize how you use your HVAC system. But like any technology, you may occasionally run into a problem. With the digital display, Honeywell smart thermostats can provide an error code that professional technicians can use to understand what's wrong. Here are some of the most likely error codes you may see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may see this error code if your home’s Wi-Fi connection did not supply an IP address for the thermostat to hook up to. This can occur if a router does not execute the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically sends out the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by confirming that your router has enabled DHCP. If it does, you may also have to power cycle the router and repeat the initial setup process with the thermostat. Completing this task should see to it that the DHCP is sent and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed whenever the password for connecting to your home’s Wi-Fi router is not correct. Once this error code appears for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can try to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear 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 alerted that a heat pump or air conditioner’s monitoring system has recognized a malfunction. For the most part, this appears once the compressor isn’t turning on despite being directed to. But this error code could also appear if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can display this error code. And finally, you could see 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, it’s best to contact an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat presents error code e43, it is failing 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

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

Error Code e1 for Honeywell Thermostats

Thermostats use sensors to detect 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 skilled technician can swap out the sensor and reboot the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

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

How to Fix Honeywell Thermostat Error 11n

A professional technician can use a voltmeter to assess if there’s a poor 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’ve noticed error code e2 show up on your Honeywell smart thermostat, it might mean a couple of different things. In some cases, one of the sensors used to detect the temperature isn’t functioning like it should. In other instances, it means the router was disconnected from power before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician should troubleshoot and switch out the impacted sensor. When the problem stems from disconnected power, all you have to do is make sure the router stays on throughout the setup process.