Nest Thermostat Error E70 — What It Means & How to Fix It

What Does This Error Mean?

Error E70 on your Nest thermostat means the thermostat cannot get a valid temperature reading from its sensors. Without a reliable temperature reading, the Nest cannot make smart heating and cooling decisions. This is often related to the thermostat's internal sensor or to communication with remote temperature sensors.

Affected Models

Nest Learning Thermostat (2nd, 3rd gen)
Nest Thermostat E
Nest Thermostat (2020 model)
Google Nest Temperature Sensor users

Common Causes

The Nest thermostat's internal temperature sensor has failed
A Nest Temperature Sensor (remote sensor) is disconnected or has a dead battery
The thermostat is in a location with extreme temperatures or drafts that confuse the sensor
A software bug in the Nest firmware is affecting sensor reading
Physical damage to the thermostat (such as from moisture) has affected the sensor

How to Fix It

Remove the Nest display from the base for 30 seconds, then reattach it.

This performs a quick hardware reset of the display sensors.
On the Nest, go to Settings > Reset > Restart to restart the software.

A software restart clears temporary sensor reading errors.
If you use Nest Temperature Sensors (the small remote sensor pucks), check the battery in each sensor. Replace with a fresh CR2032 battery if low.

A Nest Temperature Sensor with a dead battery will drop off the network and can cause temperature-related errors on the thermostat.
Check if a Nest app or system software update is available. Open the Nest or Google Home app and check for updates.

Some Nest firmware versions had sensor communication bugs that were later patched.
If the error persists, check the thermostat's installation location. It should be on an interior wall, 4–5 feet high, away from vents, sunlight, and exterior walls.

A thermostat in a drafty or exposed location may consistently read abnormal temperatures.

When to Call a Professional

If a restart, battery check, and firmware update do not resolve E70, the thermostat display may have a failed sensor and need replacement. Contact Google Nest support at support.google.com/googlenest with your serial number for warranty assessment.

Frequently Asked Questions

How do I know if my Nest Temperature Sensor battery is dead?

Open the Nest or Google Home app. Go to Settings > your Nest > Temperature Sensors. Each sensor shows its current battery level. A sensor showing 0% or 'Low Battery' needs a fresh CR2032 battery.

Can the Nest control my HVAC if it cannot read the temperature?

No — without a valid temperature reading, the Nest cannot determine when to start or stop your heating and cooling. The system will likely stay in its current state (either running or not running) until a valid reading is restored. Fix E70 promptly to avoid your home getting too hot or too cold.

Where is the best place to install a Nest thermostat to avoid sensor errors?

Mount it on an interior wall at a height of 4–5 feet. Avoid locations near the kitchen, bathroom, direct sunlight, exterior walls, or supply air vents. These locations expose the sensor to misleading temperatures. A central hallway on an interior wall is ideal for most homes.