Solved! Error Code E42 for Honeywell Smart Thermostats

A Honeywell smart thermostat is an easy way to optimize how you use your HVAC system. But like any mechanical system, you could occasionally run into a problem. With the digital display, Honeywell smart thermostats can display an error code that certified technicians use to figure out what's happening. Here are several of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Error Code e42

You might encounter this error code if your home’s Wi-Fi connection did not provide an IP address for the thermostat to connect to. This can happen if a router does not execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically sends out the needed IP address for your thermostat to link up.

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 may also have to power cycle the router and perform the setup process again with the thermostat. Doing so should see to it that the DHCP is sent and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 occurs whenever the password for accessing your home’s Wi-Fi router is not correct. When this error code is displayed for 30 seconds, the thermostat’s digital display will automatically progress 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 make sure you’re entering the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 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 often, this appears when the compressor isn’t turning on despite being directed to. But this error code may also show up if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, induced by poor airflow, can display this error code. And finally, you could experience error code 40 if there’s something wrong with the refrigerant, 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 normal operation. If you restart the thermostat and error code 40 reappears, it's time to get a hold of 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 the Wi-Fi. This could 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 a short period. The thermostat might also be disconnected if you have recently changed the password or the Wi-Fi’s SSID, which is the name you provide it.

Error Code e1 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e1

A skilled technician can replace the sensor and reboot the thermostat, which should take care of error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n may appear in situations where the thermostat can’t connect to a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is defective or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to determine if there’s a faulty electrical connection. When the wiring on your type of HVAC equipment is bad, the technician can replace it. If the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you’ve noticed error code e2 show up on your Honeywell smart thermostat, it could mean a few different things. In some cases, one of the sensors that detects the temperature isn’t working correctly. 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

When the error code is a result of sensor failure, a technician will troubleshoot and swap out the damaged sensor. If the problem stems from disconnected power, all you have to do is make sure the router remains on over the course of the setup process.