Why Is My Nest Thermostat Fan Running Constantly?
- Fan schedule set to circulate air every hour
- Thermostat set to Fan-Only mode
- Fan setting on On instead of Auto
Problem Description
Your Nest thermostat's fan runs constantly even when it isn't heating or cooling. The blower keeps going nonstop, which raises your electric bill and can make rooms feel drafty. On a Nest, continuous fan is almost always a setting — Fan set to On, a fan-circulation schedule, or Fan-Only mode — but a G-to-R wiring short, or the furnace's own fan switch set to ON, can also force it.
Why This Happens in Real Homes
A Nest fan that never stops is far more often a setting than a fault. The common causes, in order, are a fan-circulation schedule running the blower every hour, the thermostat left in Fan-Only mode, or the fan set to On instead of Auto. Each is the fan doing exactly what it was told.
Start in the Google Home app: set the fan to Auto and check the fan schedule. If it still won't stop, look at the hardware — a G (fan) wire shorted or jumpered to R, or the furnace's own fan switch set to ON, forces continuous airflow regardless of the Nest.
Symptoms
- Blower fan never shuts off
- Fan runs with no heating or cooling active
- Higher electric bill from constant fan
- Rooms feel drafty from constant airflow
- Fan runs even after changing the mode
- Fan icon shown continuously
- Fan runs on a repeating hourly cycle
- Fan will not respond to the Auto setting
Recognize these? Here's what usually causes it.
Common Causes
- Fan schedule set to circulate air every hour
- Thermostat set to Fan-Only mode
- Fan setting on On instead of Auto
- G (fan) wire shorted or jumpered to R at the base
- Furnace/air-handler fan switch set to ON not AUTO
- Airwave running the fan after a cooling cycle
- Continuous fan enabled intentionally for filtration
- Miswired G terminal after a thermostat swap
Most fixes happen in the first 3 steps.
Always turn off your HVAC system at the breaker before removing the thermostat or touching wires. Incorrect wiring can damage both the thermostat and your HVAC equipment resulting in expensive repairs. If unsure about wiring consult an HVAC technician.
Tools & Requirements
These tools will help you complete this fix.
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Step-by-Step Solution
Check the fan schedule setting
The Nest thermostat has a fan schedule that runs the fan independently of heating or cooling. In the Google Home app, select the thermostat and check the fan settings. If the fan is set to run on a schedule (for example, 15 minutes per hour for air circulation), it will run even when no heating or cooling is active. Reduce or disable the fan schedule if you do not want it running.
Check if the system is in fan-only mode
If someone set the thermostat to fan-only mode (no heating or cooling, just fan circulation), the fan runs continuously. Check the thermostat display or the Google Home app for the current mode. Switch to Heat, Cool, or Heat/Cool mode instead of Fan Only. Fan Only is useful for air circulation but runs the fan non-stop.
Check for a wiring issue
If the fan runs constantly regardless of thermostat settings, the G wire (fan control) may be shorted to the R wire (power) in the wiring. This sends continuous power to the fan relay, bypassing the thermostat. Turn off the HVAC breaker, pull the Nest off the base, and check for wires touching or a pinched wire in the wall. Also check the furnace control board for the G terminal connection.
Check the HVAC system fan setting
Some HVAC systems have a fan switch on the furnace or air handler set to ON instead of AUTO. This switch overrides the thermostat — the fan runs continuously regardless of what the Nest says. Locate the furnace or air handler and check for a fan switch. Set it to AUTO so the thermostat controls the fan.
Consider if continuous fan is intentional
Some homeowners set the fan to run continuously for better air filtration, even temperature distribution, or to reduce humidity. If someone else in your household configured this intentionally, check before changing it. Running the fan continuously costs about $15-50 per month in electricity depending on your motor type. Variable-speed fan motors use much less power when running continuously compared to single-speed motors.
Quick Solutions
Still having issues? This is usually the deeper cause below.
Schedules that skip randomly are usually a daylight-saving holdover — delete and recreate the schedule to clear the corrupted entry.
Use the thermostat energy reports to find patterns in your heating and cooling usage. Setting back the temperature just 3 degrees when you leave for work can save 5 to 10 percent on your annual energy bill without any comfort sacrifice. **Product Intelligence:** - C-wire required for most models - 2.4GHz WiFi only - Nest Aware subscription for history
Thermostat issues that keep returning are often caused by stale backup-battery memory holding old settings across power cycles without the user realising.
- Fan schedule set to circulate air every hour
- Thermostat set to Fan-Only mode
- Fan setting on On instead of Auto
- G (fan) wire shorted or jumpered to R at
- Furnace/air-handler fan switch set to ON not AUTO
Before you go — try one of these (they fix most cases).
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Official Manufacturer Manual
Google Nest provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Nest Thermostat.
Source: google.com
Need More Help? Google Nest Support
Note: The contact information below connects you directly to Google Nest's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
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