A Honeywell smart thermostat is a great way to better manage how you use your heating and cooling. But like any utility, you could sometimes run across a problem. With its digital display, Honeywell smart thermostats can provide an error code that professional technicians use to figure out what's going on. Here are some of the most known error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can encounter this error code in the event that your home’s Wi-Fi connection did not provide an IP address for the thermostat to connect to. This can happen if your router does not perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically transmits the necessary 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 confirming that your router can complete the DHCP. When it does, you might also need to power cycle the router and repeat the initial setup process with the thermostat. Doing so should ensure the DHCP is delivered and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 occurs whenever the password for connecting to your home’s Wi-Fi router is incorrect. When this error code appears for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to clear error e02 is verify you’re typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can pop 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 occurs once the compressor isn’t turning on despite being instructed to. But this error code may also show up if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by obstructed airflow, can render this error code. Lastly, you could 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 normal operation. If you turn the thermostat off and on again and error code 40 reappears, it's time to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If a Honeywell thermostat shows error code e43, it is unable to communicate with the router, and by extension the 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

Reset the router by unplugging it and leaving it that way for a short period. The thermostat may also be disconnected if you have recently updated the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Error Code e1

Thermostats use sensors to identify the temperature outdoors and indoors. If a sensor fails, you might notice error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Honeywell Thermostat Error 11n

Error code 11n could appear when the thermostat is failing to connect to a heating or cooling unit. This might 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 qualified technician can utilize a voltmeter to assess if there’s a bad electrical connection. In situations where the wiring on your specific HVAC equipment is bad, the technician can replace it. If the thermostat itself is the problem, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 show up on your Honeywell smart thermostat, it might mean a few different things. Sometimes, one of the sensors that detects the temperature isn’t operating correctly. In other cases, it means the router was disconnected from power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician can troubleshoot and replace the impacted sensor. When the problem stems from disconnected power, all you'll need to do is make sure the router stays on throughout the setup process.