What does error code E5 mean on a Google Nest thermostat?

No heating or cooling wire detected. No heating or cooling was detected. A W1 or Y1 wire is required.

Can I fix Google Nest code E5 myself?

Start with these safe checks: With power off, check the W1 and Y1 wires are fully inserted. Compare your wiring to the diagram in the app. If unsure about wiring, have a pro check it.

When should I call a technician for code E5?

If unsure about wiring, have a pro check it. 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 E5 / E25 / E75: No heating or…

What E5 means

No heating or cooling was detected. A W1 or Y1 wire is required.

Also shown as: E25, E75, E155, E255, E405, depending on the model.

Likely causes

W1/Y1 wire missing or not seated

Safe first checks

With power off, check the W1 and Y1 wires are fully inserted.
Compare your wiring to the diagram in the app.

When to stop

If unsure about wiring, have a pro check it.

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