Google Nest error codes and warnings
Match the exact device and display before troubleshooting. These independent guides begin with published manufacturer information and keep the safe owner checks separate from service work.
HVAC & Thermostats
Nest Thermostat E73 Error: No Power to Rc Meaning
E73 means the thermostat is not detecting power on the Rc cooling-power wire. Check system power before touching wiring.
Read the guideNest Thermostat E74 Error: No Power to Rh Meaning
E74 means the thermostat is not detecting power on the Rh heating-power wire. Start with breakers and the furnace service switch.
Read the guideNest Thermostat E195 Error: No Power Meaning and Safe Checks
E195 is a thermostat power problem. Verify the HVAC breaker, equipment switch, and obvious shutdown conditions.
Read the guideNest Thermostat E52 Error: W1 Overcurrent Meaning
The thermostat detected repeated current spikes on the W1 circuit. Correct wiring or HVAC control-board service may be required.
Read the guideNest Thermostat E53 Error: Y1 Overcurrent Meaning
The thermostat detected repeated current spikes on the Y1 circuit. Correct wiring or HVAC control-board service may be required.
Read the guideNest Thermostat E298 Error: No Power Alert Meaning
These codes indicate a no-power alert. Confirm HVAC power and allow the thermostat time to recover after power is restored.
Read the guideNest Thermostat W5 Error: Wi-Fi Hardware Meaning and Fixes
W5 means the thermostat cannot connect to Wi-Fi and may have a hardware fault. Confirm the actual W5 code, then restart once.
Read the guideNest Thermostat E79 Error: No Power to C Wire
The thermostat is not detecting power on the common wire. Turn HVAC power off before checking the C connection.
Read the guideNest Thermostat E80 Error: No Power to Y1
The thermostat is not receiving expected power through Y1. This can follow an HVAC shutdown and may need professional diagnosis.
Read the guideNest Thermostat E77 Error: Y1 Wire Not Detected
A required Y1 cooling or heat-pump wire is not detected. Record the existing wiring before any correction.
Read the guideNest Thermostat E78 Error: Additional Wire Required
The detected W2/AUX configuration requires another compatible wire or corrected setup. Do not move conductors based on color alone.
Read the guideNest Thermostat M22 Offline: Connection Meaning
The thermostat is offline from the app. Confirm local operation and home Wi-Fi before reconnecting it.
Read the guideA nearby code is not necessarily the same code.
Confirm the model number and complete display in the official manual. If the code is missing, send us the brand, model, and exact warning.