Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is a great way to optimize how you use your HVAC system. But like any mechanical system, you may sometimes run across a problem. With the digital display, Honeywell smart thermostats can show an error code that trained technicians use to understand what's going on. Here are a few of the most likely error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You might see this error code in the event that your home’s Wi-Fi connection did not provide an IP address for the thermostat to connect with. This can take place if a router does not perform 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 may 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 sent and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 appears whenever the password for accessing your home’s Wi-Fi router is not correct. After 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 to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to solve error e02 is make sure you’re putting in the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this appears once the compressor isn’t turning on despite being instructed to. But this error code can 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 poor airflow, can lead to this error code. Finally, you may see error code 40 if there’s an issue 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 turn the thermostat off and on again and error code 40 reappears, it's time to contact an experienced technician.

Honeywell Thermostat Error e43

If your 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 may also be disconnected if you have recently changed the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Thermostat Error e1

Thermostats use sensors to detect the temperature outdoors and indoors. If a sensor fails, 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 reboot the thermostat, which should take care of error code e1.

Honeywell Error Code 11n

Error code 11n can appear when the thermostat is unable to recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning 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 qualified technician can employ a voltmeter to assess if there’s a bad electrical connection. If the wiring on your type of HVAC equipment is bad, the technician can replace it. In situations where the thermostat itself is the issue, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 appear on your Honeywell smart thermostat, it might mean a couple of different things. Sometimes, one of the sensors that detects the temperature isn’t functioning like it should. In other instances, it means the router was disconnected from its power source before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician should troubleshoot and switch out the damaged sensor. If the problem originates from disconnected power, all you'll need to do is see to it that the router stays on throughout the setup process.