Article Summary:
If you get an error code numbered between E52 and E58 or between E102 and E108, there are some simple things to check. Here’s how to troubleshoot these errors.

You may get a wiring error when first installing your Nest Learning Thermostat or one may pop up after you've been using your thermostat for some time. Depending on when you get the error, the troubleshooting steps are different.

If you installed a Nest Thermostat a while ago

If your Nest Thermostat was installed successfully and you've been using it for a while, and an error between E52 to E58 or E102 to E108 pops up, there might be something wrong with your HVAC system, not the thermostat wiring.

If seasons have changed, then an error may have happened when you switched your system between heating and cooling. Also, if you've had recent HVAC system maintenance or an upgrade, then there may have been a problem that was undetected during testing. In this case, please contact us, or call your installer or local HVAC professional.

If you are installing a Nest Thermostat

If you get one of the error codes listed in the table below when installing the Nest Thermostat, usually it's because the wrong wire is inserted into one of the connectors. Check the table below to identify the wire that's causing the error. Then follow the troubleshooting steps.

Here's a list of the error numbers and the corresponding wire that you'll need to check:

Error Code

Wire to check

E52 & E102

W1

E53 & E103

Y1

E54 & E104

G

E55 & E105

O/B

E56 & E106

W2/Aux

E57 & E107

Y2

E58 & E108

*

Troubleshooting steps

• Remove the Nest Thermostat display and confirm that the wires are connected the same way as they were to your old thermostat. If you took a picture of your old thermostat wiring during installation, please refer to it.
• If your old thermostat had 2 labels for each connector, double check that you've put the correct labels on the wires. For detailed help, please see the following article: My old thermostat has two labels for each connector
• If you have separate wires for Rh and Rc, make sure that they are inserted into the right connectors. They can get mixed up during installation.
• Make sure the "wire to check" (noted above according to the error number) isn't a common 'C' wire. If the wire turns out to be a common 'C' wire, move it to the 'C' connector in the Nest base. For detailed help, please see the following article: How to tell if your B wire is really a common wire in disguise
• The majority of E55 & E105 errors are caused by a C wire being mislabeled as a B wire. If you determine the wire in the O/B connector is a common 'C' wire, move it to the 'C' connector in the Nest base.

What do the Nest Learning Thermostat's error codes mean? >

If you’ve verified that your wiring is correct, but you’re still getting one of these errors, please contact us. We’re here 24/7. Take a photo of your thermostat wiring, and have it ready to send to us when you call.