What does error code E299 mean on a Google Nest thermostat?

Contact Nest support. Google says you need to contact Nest customer support for this one.

Can I fix Google Nest code E299 myself?

Start with these safe checks: Have the code and serial number (on the back of the display, above the QR code) ready. Contact Google Nest support.

When should I call a technician for code E299?

Contact Google Nest support. Thermostat wiring is low voltage, but switch the HVAC system off at its breaker or service switch before pulling the thermostat off the wall. If the code points to the furnace or outdoor unit, leave gas, combustion and refrigerant parts to a licensed HVAC technician.

Google Nest Thermostat Error Code E299 / M24: Contact Nest support

What E299 means

Google says you need to contact Nest customer support for this one.

Also shown as: M24, depending on the model.

Likely causes

Device issue

Safe first checks

Have the code and serial number (on the back of the display, above the QR code) ready.

When to stop

Contact Google Nest support.

Checked against: Google Nest Help: Troubleshoot Nest thermostat help codes. Codes can differ by model and year, so confirm with your owner's manual.