A Honeywell smart thermostat is a great way to optimize how you use your HVAC system. But like any technology, you might sometimes experience a problem. With a digital display, Honeywell smart thermostats can show an error code that certified technicians use to understand what's happening. Here are some of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Error Code e42

You may encounter this error code in the event that 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 does not perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the required IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router can complete the DHCP. When it does, you might also need to power cycle the router and perform the setup process again with the thermostat. This should see to it that the DHCP is sent 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 not correct. 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 attempt 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 putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has identified a malfunction. For the most part, this happens when the compressor isn’t running despite being directed to. But this error code can also show up if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by blocked airflow, can lead to this error code. And finally, 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 check the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for ordinary operation. If you restart the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If a Honeywell thermostat displays error code e43, it can’t communicate with the router, and by extension your 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

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

Error Code e1 for Honeywell Thermostats

Thermostats use sensors to determine the temperature outdoors and indoors. If a sensor malfunctions, you could see error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can replace the sensor and reset the thermostat, which should take care of error code e1.

Honeywell Error Code 11n

Error code 11n may appear if the thermostat can’t connect to a heating or cooling unit. This might mean that the equipment itself is faulty and unable to communicate 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 find out if there’s a poor electrical connection. If the wiring on your existing HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Error Code e2

If you notice error code e2 pop up on your Honeywell smart thermostat, it might mean several different things. For example, one of the sensors that detects the temperature isn’t working properly. 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

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