A Honeywell smart thermostat is an easy way to optimize how you use your heating and cooling. But like any utility, you may occasionally experience a problem. With the digital display, Honeywell smart thermostats can display an error code that trained technicians can use to get a better sense of what's wrong. Here are a few of the most common error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

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

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by making sure that your router can complete the DHCP. Assuming it does, you may also have to power cycle the router and repeat the initial setup process with your thermostat. Completing this task should see to it that the DHCP is delivered and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 is displayed if the password for accessing your home’s Wi-Fi router is incorrect. When 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 need to do to clear error e02 is ensure you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can appear when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most commonly, this appears if the compressor isn’t working despite being directed to. But this error code may also appear if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by poor airflow, can display this error code. 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 check the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular operation. If you restart the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Honeywell Thermostat Error e43

If your Honeywell thermostat displays error code e43, it can’t communicate with the router, and by extension your Wi-Fi. This may 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 a short period. The thermostat may also be disconnected if you’ve recently switched the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats utilize sensors to identify the temperature outdoors and indoors. If a sensor malfunctions, you might see error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can replace the sensor and reset the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

Error code 11n could appear if the thermostat can’t recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to communicate with the thermostat. This sometimes happens when the wiring is bad or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to find out if there’s a poor electrical connection. In situations where the wiring on your existing HVAC equipment is bad, the technician can replace it. If the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 pop up on your Honeywell smart thermostat, it can mean several different things. For example, one of the sensors used to detect the temperature isn’t functioning correctly. In other cases, 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

When the error code stems from sensor failure, a technician should troubleshoot and replace the affected sensor. When the problem stems from disconnected power, all you’ll have to do is see to it that the router stays on throughout the setup process.