Solved! Error Code E42 for Honeywell Smart Thermostats

A Honeywell smart thermostat is an easy way to optimize how you use your heating and cooling. But like any utility, you could sometimes experience a problem. With a digital display, Honeywell smart thermostats can show an error code that certified technicians will use to understand what's happening. Here are some of the most common error codes you could see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can receive this error code if your home’s Wi-Fi internet did not supply an IP address for the thermostat to connect with. This can occur if your router doesn't execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the needed 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 is enabled for DHCP. Assuming it does, you might also need 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.

Error Code e02 for Honeywell Thermostats

Error code e02 is displayed if the password for communicating with your home’s Wi-Fi router is incorrect. Once this error code has appeared for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to clear error e02 is ensure you’re typing the correct Wi-Fi password when configuring 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 happens when the compressor isn’t working despite being directed to. But this error code could also show up if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. Lastly, you may experience error code 40 if there’s something wrong 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 ordinary operation. If you reset the thermostat and error code 40 reappears, it's time to contact an experienced technician.

Honeywell Error Code e43

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

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

Honeywell Thermostat Error e1

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

How to Fix Honeywell Thermostat Error e1

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

Error Code 11n for Honeywell Thermostats

Error code 11n may appear in situations where the thermostat is failing to recognize a heating or cooling unit. This can mean that the equipment itself is defective and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to determine if there’s a bad electrical connection. In situations where the wiring on your specific HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the source of the error code, it should probably be replaced.

Honeywell Thermostat Error e2

If you notice error code e2 appear on your Honeywell smart thermostat, it might mean a couple of different things. In some cases, one of the sensors that detects the temperature isn’t operating properly. Other times, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is caused by sensor failure, a technician can troubleshoot and replace the damaged sensor. Any time the problem stems from disconnected power, all you’ll have to do is make sure the router stays on over the course of the setup process.