🌡️Thermostat

FAN-CONSTANT

Ecobee · ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included

Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included FAN-CONSTANT Error Fix: Fan Running Constantly

The HVAC fan runs nonstop even when not calling for heating or cooling — check that the fan setting is set to Auto (not On) in the thermostat, verify the G-wire (fan) connection, and check if a stuck fan relay on the HVAC control board is keeping the fan energized

Medium severity2 fixes available✨ Free fix available

Quick Answer

Error FAN-CONSTANT on the Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included means: Fan Running Constantly. The top-ranked community fix is “Test and Replace HVAC Control Board Fan Relay” (hard difficulty, ~60 min, DIY cost: $10-$20). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · thermostat

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many thermostat repairs can be done safely at home, consider hiring a qualified technician if:

The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $150-$250.

Other Ecobee Models with Error FAN-CONSTANT

ecobee Smart Thermostat Enhanced with Radar Occupancy Sensor and Large Touchscreen

thermostat · 2 fixes

ecobee Smart Thermostat Essential with Touchscreen Display and eco+ Smart Features

thermostat · 2 fixes

ecobee SmartThermostat with Voice Control and Alexa Built-In

thermostat · 2 fixes

ecobee3 Lite Smart Thermostat

thermostat · 2 fixes

ecobee4 Smart Thermostat

thermostat · 2 fixes

Other Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included Error Codes

AIR-QUALITY

Air Quality Alert

2 fixes

APP-SYNC

App and Thermostat Out of Sync

2 fixes

AUX-OUTDOOR

Auxiliary Heat Outdoor Temperature Alert

2 fixes

AUX-RUNTIME

Auxiliary Heat Runtime Alert

2 fixes

BLOWN-FUSE

HVAC Control Board Fuse Blown

2 fixes

COOL-FAIL

Cool Not Reaching Set Temperature

2 fixes

FILTER-REMIND

Furnace Filter Reminder

2 fixes

HEAT-FAIL

Heat Not Reaching Set Temperature

2 fixes

People Also Ask About Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included Error FAN-CONSTANT

What does error code FAN-CONSTANT mean on a Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included?

Error code FAN-CONSTANT on the Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included means: Fan Running Constantly. The HVAC fan runs nonstop even when not calling for heating or cooling — check that the fan setting is set to Auto (not On) in the thermostat, verify the G-wire (fan) connection, and check if a stuck fan relay on the HVAC control board is keeping the fan energized

How do I fix error code FAN-CONSTANT on my Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included?

The most successful fix is "Test and Replace HVAC Control Board Fan Relay" (hard difficulty, ~60 minutes). Estimated DIY cost: $10-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code FAN-CONSTANT on a Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included serious?

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Can I fix Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included error FAN-CONSTANT myself?

Yes — the top-ranked community fix ("Test and Replace HVAC Control Board Fan Relay") is rated hard difficulty and takes about 60 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Needle-nose pliers.

How much does it cost to repair Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included error FAN-CONSTANT?

DIY cost: $10-$20. Professional repair typically costs $150-$250. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included have?

The Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included has 8 other known error codes, including: AIR-QUALITY (Air Quality Alert), APP-SYNC (App and Thermostat Out of Sync), AUX-OUTDOOR (Auxiliary Heat Outdoor Temperature Alert), AUX-RUNTIME (Auxiliary Heat Runtime Alert), BLOWN-FUSE (HVAC Control Board Fuse Blown), and 3 more.

Which other Ecobee models have the FAN-CONSTANT error?

Error code FAN-CONSTANT also appears on 5 other Ecobee models: ecobee Smart Thermostat Enhanced with Radar Occupancy Sensor and Large Touchscreen, ecobee Smart Thermostat Essential with Touchscreen Display and eco+ Smart Features, ecobee SmartThermostat with Voice Control and Alexa Built-In, ecobee3 Lite Smart Thermostat, ecobee4 Smart Thermostat. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included have?

The Ecobee ecobee Smart Thermostat Premium with Siri and Alexa Built-In, Air Quality Monitor, and SmartSensor Included has 8 other known error codes:

AIR-QUALITY — Air Quality Alert (2 fixes)
APP-SYNC — App and Thermostat Out of Sync (2 fixes)
AUX-OUTDOOR — Auxiliary Heat Outdoor Temperature Alert (2 fixes)
AUX-RUNTIME — Auxiliary Heat Runtime Alert (2 fixes)
BLOWN-FUSE — HVAC Control Board Fuse Blown (2 fixes)
COOL-FAIL — Cool Not Reaching Set Temperature (2 fixes)
FILTER-REMIND — Furnace Filter Reminder (2 fixes)
HEAT-FAIL — Heat Not Reaching Set Temperature (2 fixes)

Which other Ecobee models have the FAN-CONSTANT error?

Error code FAN-CONSTANT also appears on 5 other Ecobee models:

ecobee Smart Thermostat Enhanced with Radar Occupancy Sensor and Large Touchscreen (thermostat) · 2 fixes
ecobee Smart Thermostat Essential with Touchscreen Display and eco+ Smart Features (thermostat) · 2 fixes
ecobee SmartThermostat with Voice Control and Alexa Built-In (thermostat) · 2 fixes
ecobee3 Lite Smart Thermostat (thermostat) · 2 fixes
ecobee4 Smart Thermostat (thermostat) · 2 fixes

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