Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is an excellent way to fine-tune how you use your heating and cooling. But like any utility, you might sometimes run across a problem. With a digital display, Honeywell smart thermostats can show an error code that trained technicians use to get a better sense of what's going on. Here are several of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may receive this error code in the event that your home’s Wi-Fi internet did not provide an IP address for the thermostat to connect with. This can take place if the router does not execute the Dynamic Host Configuration Protocol, or DHCP. This process automatically sends out the required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

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

Error Code e02 for Honeywell Thermostats

Error code e02 occurs when the password for accessing your home’s Wi-Fi router was incorrect. After this error code has appeared 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 make sure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has identified a malfunction. For the most part, this appears if the compressor isn’t turning on despite being instructed to. But this error code may also appear if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by blocked airflow, can lead to this error code. And finally, you might experience 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 inspect 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, you should try to get a hold of an experienced technician.

Error Code e43 for Honeywell Thermostats

If a 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

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

Honeywell Error Code e1

Thermostats utilize sensors to determine the temperature outdoors and indoors. If a sensor malfunctions, you could see error code e1 turn 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.

Error Code 11n for Honeywell Thermostats

Error code 11n can appear in situations where the thermostat is unable to connect to a heating or cooling unit. This might mean that the equipment itself is faulty and unable to connect with the thermostat. This can happen when the wiring is defective or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A professional technician can use a voltmeter to determine if there’s a bad electrical connection. When 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 will likely have to be replaced.

Honeywell Thermostat Error e2

If you see error code e2 show up 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 operating like it should. In other cases, it means the router was disconnected from power 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 will troubleshoot and switch out the damaged sensor. If the problem comes from disconnected power, all you'll need to do is verify the router remains on over the course of the setup process.