Nest Thermostat Error W5 — What It Means & How to Fix It

What Does This Error Mean?

Nest error W5 means your heating or cooling system has been temporarily disabled. The Nest detected a condition that caused it to pause the system to protect your HVAC equipment. This is a protective measure — the Nest is not broken, but your heating or cooling will not run until the issue is resolved.

Affected Models

Nest Learning Thermostat (2nd gen, 3rd gen)
Nest Thermostat E
Google Nest Thermostat (2020)

Common Causes

The Nest detected short cycling — the system was turning on and off too rapidly
The HVAC system just ran and the Nest is in a mandatory delay period before restarting
A wiring issue is causing the Nest to detect an unusual signal from the HVAC system
The outdoor temperature is outside the safe operating range for your heat pump
An error code or lockout condition on the HVAC control board has paused the system

How to Fix It

Wait up to 5 minutes. The W5 alert often appears during a normal protection delay after your system last ran. The Nest prevents systems from restarting too quickly to protect compressors.

This delay is called 'compressor protection' and is normal behavior — not a fault.
Check your air filter. A clogged filter restricts airflow and causes the system to overheat or short cycle. Locate the filter in your air handler or return vent and replace it if dirty.

A dirty filter is one of the most common causes of HVAC system lockouts and errors.
Check your HVAC unit for any error lights or codes. The air handler or outdoor unit may have its own diagnostic display with a more specific error code.

Look for a small blinking LED on the control board inside the air handler, or a display on the outdoor unit.
Restart the Nest thermostat. Press and hold the thermostat ring for 10 seconds until the screen goes off, then release. The Nest will restart and re-evaluate the system status.

A restart clears temporary fault states and lets the Nest reconnect to the HVAC system fresh.
Check the HVAC circuit breaker. A tripped breaker for the air handler or outdoor unit can cause the Nest to detect a system fault and show W5. Reset any tripped breakers.

If the breaker trips again immediately, there is a serious electrical issue — call a professional.

When to Call a Professional

If the W5 message does not clear within 30 minutes and your HVAC system still will not run, call an HVAC technician. Short cycling that caused the W5 may indicate a refrigerant problem, a blocked filter, or a failing compressor. These issues require professional diagnosis and cannot be fixed by adjusting the thermostat.

Frequently Asked Questions

How long does the W5 delay last?

The W5 compressor protection delay usually lasts between 2 and 5 minutes. If the message is still showing after 30 minutes, there is likely a deeper HVAC issue. Do not keep adjusting the temperature trying to force the system on — let it complete the delay.

Is the W5 warning dangerous?

Not directly — it is a protective feature, not a sign of a crisis. However, if it is triggered repeatedly by short cycling, the underlying cause (like low refrigerant) can damage your compressor over time. Address the root cause as soon as possible.

Can I override the W5 delay?

You cannot bypass the compressor protection delay — it is built into the Nest for safety. Forcing a compressor to restart too soon can cause serious damage. The best approach is to wait and then investigate if the error persists beyond 30 minutes.