Solved! Error Code E42 for Honeywell Smart Thermostats

A Honeywell smart thermostat is a great way to optimize how you use your heating and cooling. But like any mechanical system, you may sometimes experience a problem. With its digital display, Honeywell smart thermostats can provide an error code that certified technicians use to understand what's wrong. Here are some of the most known error codes you may see on your Honeywell smart thermostat.

Honeywell Error Code e42

You can see this error code if your home’s Wi-Fi internet did not present an IP address for the thermostat to hook up to. This can occur if a router doesn't complete the Dynamic Host Configuration Protocol, or DHCP. This function 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 has enabled DHCP. Assuming it does, you may also need to power cycle the router and perform the setup process again with the thermostat. Completing this task should ensure the DHCP is sent and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 appears if the password for communicating with your home’s Wi-Fi router is incorrect. Once 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 attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear 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 alerted that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this occurs once the compressor isn’t running despite being instructed to. But this error code could also show up if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, triggered by blocked airflow, can render this error code. Lastly, you may see 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 inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for ordinary operation. If you turn the thermostat off and on again and error code 40 reappears, you should try to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If the 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

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

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

A qualified technician can replace the sensor and reset the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if 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 professional technician can utilize a voltmeter to determine if there’s a faulty electrical connection. In situations where the wiring on your existing HVAC system is bad, the technician can replace it. If the thermostat itself is the issue, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it can mean a couple of different things. Sometimes, one of the sensors used to detect the temperature isn’t functioning properly. In other cases, it means the router was disconnected from the outlet before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code is caused by sensor failure, a technician can troubleshoot and swap out the damaged sensor. Any time the problem comes from disconnected power, all you'll need to do is see to it that the router remains on over the course of the setup process.