How to fix Honeywell Thermostat E43 Error Code

A Honeywell thermostat e43 error code indicates that your thermostat can not communicate with a hotspot or router serving it with the LAN (Local Area network) or Internet. Fixing the problem will often require a reboot of the router or thermostat and ensuring that the router wifi password is correct.

In this troubleshooting guide, we are going to look at what causes your honeywell thermostat to display an e43 error code and what you can do to reset this error code.

Honeywell thermostat e43 code causes and how to reset it

Possible Cause	How to Reset the code
Router is off	Turn on the router
Wrong wifi password	Try re-entering password on your thermostat
Router firmware glitch	Restart/ reset the router
Router is not connected to WAN	Ensure that the ethernet cable is connected and undamaged
Thermostat Wifi settings needs a reset	Restart reset thermostats wifi settings

Now let’s look at each of the above causes and how to reset the e43 code in a little more details.

Router is Off

The router acts as the gateway between your thermostat’s internet connectivity and the WAN(wide Area network). This means that a thermostat has to get connected to a router that is turned on.

If the router is turned off, the thermostat wont simply connect and that is a valid reason you have an e43 error code displayed on your thermostat.

Wrong Wifi/Password

Another reason your thermostat is displaying the e43 code could be that the thermostat wifi password you entered is not correct. This is especially the case if you recently changed the password or got a new router.

Try connecting another device to the router such as your phone or tablet. If you are able to connect to your router with another device, chances are, the wifi password on the thermostat is incorrect.

Router firmware glitch

If you have confirmed that the wifi password is correct but the thermostat still can not connect to the router, is the right time to restart your router. But because with a router reset you might lose all settings and configurations. Reset it to factory defaults only if you can reconfigure it yourself.

To restart the router unplug it from the socket for about 15 seconds.

Router is not connected to WAN

When the router has issues connecting to your wide Area Network WAN you might as well experience the connection error code. This issue is a common cause for the honeywell thermostat offline message. In this case ensure that ethernet cables are properly connect and undamaged

Thermostat Wifi settings needs a reset

To reset the thermostat’s Wi-Fi settings

Press and hold the Fan Button and Up Arrow for about 5 seconds to change the screen.
Press Back Button or Next Button until 39 appears on the left.
Press the Up or Down Arrows to change the number on the right to 0.
Press Done Button.
“Wi-Fi Setup” will appear on the thermostat screen after 1-2 minutes.

Final thoughts

In conclusion, troubleshooting and fixing the Honeywell thermostat E43 error code can be done through basic steps such as restarting your router or re-entering the wifi password. However, if the problem persists, it’s advisable to seek professional assistance from an HVAC technician or contact Honeywell customer support for further guidance.

Read: What Does Reco Mean On Thermostat?

See also: How to troubleshoot connection failure on honeywell thermostat