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

Honeywell Thermostat Error e42

You can see this error code in the event that your home’s Wi-Fi internet did not provide an IP address for the thermostat to hook up to. This can take place if a router does not complete the Dynamic Host Configuration Protocol, or DHCP. This process automatically sends out the needed IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router can complete the DHCP. If it does, you usually also need to power cycle the router and repeat the initial setup process with the thermostat. This should see to it that the DHCP is delivered and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 occurs when the password for communicating with your home’s Wi-Fi router is not correct. When this error code is displayed for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to resolve error e02 is make sure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can pop up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most often, this appears when the compressor isn’t working despite being directed 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, induced by blocked airflow, can lead to 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, you should try to contact an experienced technician.

Honeywell Thermostat Error e43

If your Honeywell thermostat presents error code e43, it is failing to 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 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 have recently updated the password or the Wi-Fi’s SSID, which is the name you give it.

Honeywell Error Code e1

Thermostats employ 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 skilled technician can swap out the sensor and restart the thermostat, which should take care of error code e1.

Honeywell Error Code 11n

Error code 11n can appear when the thermostat is failing to recognize a heating or cooling unit. This may mean that the equipment itself is defective and unable to communicate with the thermostat. This sometimes happens when the wiring is defective or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to determine if there’s a bad electrical connection. When the wiring on your specific HVAC equipment is bad, the technician can replace it. If the thermostat itself is the problem, it should probably be replaced.

Honeywell Error Code e2

If you notice error code e2 appear on your Honeywell smart thermostat, it could mean a couple of different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t working properly. In other cases, it means the router was disconnected from its power source 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 will troubleshoot and swap out the impacted sensor. Any time the problem originates from disconnected power, all you have to do is verify the router remains on over the course of the setup process.