A Honeywell smart thermostat is a great way to fine-tune how you use your home comfort system. But like any mechanical system, you may occasionally run into a problem. With its digital display, Honeywell smart thermostats can show an error code that professional technicians can use to understand what's going on. Here are some of the most common error codes you might see on your Honeywell smart thermostat.

Honeywell Error Code e42

You might receive this error code when your home’s Wi-Fi internet did not supply an IP address for the thermostat to hook up to. This can occur if your router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the necessary IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router can complete the DHCP. When it does, you might also have to power cycle the router and complete the initial setup process again with the thermostat. Doing so should ensure the DHCP is transmitted and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed if the password for connecting to your home’s Wi-Fi router is not correct. After 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 to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to solve error e02 is ensure you’re typing the correct Wi-Fi password when setting up the thermostat.

Honeywell Error Code 40

Error code 40 can appear when the thermostat is informed that a heat pump or air conditioner’s monitoring system has identified a malfunction. Most often, this occurs once the compressor isn’t running despite being instructed to. But this error code could also surface if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by blocked airflow, can display this error code. Lastly, you may see 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 inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular 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 a Honeywell thermostat shows error code e43, it is failing to communicate with the router, and by extension the Wi-Fi. This could 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

Restart the router by unplugging it and leaving it that way for around 30 seconds. The thermostat could also be disconnected if you’ve 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 fails, you may notice error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can change out the sensor and reset the thermostat, which should resolve error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear if the thermostat can’t detect a heating or cooling unit. This might mean that the equipment itself is defective 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 find out if there’s a bad electrical connection. If the wiring on your specific 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.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 pop up on your Honeywell smart thermostat, it might mean a couple of different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t functioning correctly. In other cases, it means the router was disconnected from its power source before the thermostat completed 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 swap out the affected sensor. When the problem originates from disconnected power, all you have to do is see to it that the router stays on during the setup process.