A Honeywell smart thermostat is an easy way to optimize how you use your HVAC system. But like any mechanical system, you could sometimes run across a problem. With a digital display, Honeywell smart thermostats can display an error code that professional technicians can use to understand what's happening. Here are some of the most likely error codes you could 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 internet did not supply an IP address for the thermostat to connect to. This can take place if your router does not perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically sends out the required IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

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

Honeywell Thermostat Error e02

Error code e02 appears when the password for communicating with your home’s Wi-Fi router is incorrect. When this error code appears for 30 seconds, the thermostat’s digital display will automatically progress 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 typing the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can appear when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this appears when the compressor isn’t turning on despite being directed to. But this error code could also appear if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can lead to this error code. Lastly, you might 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 examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you reset the thermostat and error code 40 reappears, it’s best to get in touch with an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat shows error code e43, it is unable to communicate with the router, and by extension your Wi-Fi. This might 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

Reset the router by unplugging it and leaving it that way for a short period. The thermostat could 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 Thermostat Error e1

Thermostats utilize sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you might see error code e1 appear 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 Thermostat Error 11n

Error code 11n can appear when the thermostat can’t detect a heating or cooling unit. This may mean that the equipment itself is faulty 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 determine if there’s a bad electrical connection. In situations where the wiring on your specific HVAC equipment is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 pop up on your Honeywell smart thermostat, it could mean several different things. For example, one of the sensors responsible for detecting the temperature isn’t operating like it should. Other times, it means the router was disconnected from the outlet before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is caused by sensor failure, a technician should troubleshoot and switch out the impacted sensor. If the problem stems from disconnected power, all you have to do is see to it that the router stays on over the course of the setup process.