Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is an easy way to fine-tune how you use your HVAC system. But like any utility, you might sometimes run across a problem. With its digital display, Honeywell smart thermostats can show an error code that professional technicians will use to get a better sense of 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 may receive 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 happen if a router fails to complete the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the needed IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by making sure that your router has enabled DHCP. If it does, you may also need to power cycle the router and perform the setup process again with the thermostat. This should ensure the DHCP is transmitted and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 occurs if the password for accessing your home’s Wi-Fi router is not correct. After this error code has appeared 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 resolve error e02 is make sure you’re entering the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this appears if the compressor isn’t working despite being directed 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, triggered by blocked airflow, can lead to this error code. Lastly, you might encounter 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 check 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 in touch with an experienced technician.

Honeywell Error Code e43

If your Honeywell thermostat displays 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

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

Error Code e1 for Honeywell Thermostats

Thermostats utilize sensors to determine the temperature outdoors and indoors. If a sensor breaks down, 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 reset the thermostat, which should take care of error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear in situations where the thermostat is failing 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 damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

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

Honeywell Error Code e2

If you’ve noticed error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. For example, one of the sensors responsible for detecting the temperature isn’t operating like it should. In other instances, it means the router was disconnected from the outlet before the thermostat completed 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 impacted sensor. When the problem stems from disconnected power, all you have to do is make sure the router stays on during the setup process.