ecobee3 lite Thermostat Not Heating or Cooling

The ecobee3 lite is a WiFi-connected smart thermostat that works with most HVAC systems. This guide covers common heating, cooling, and connectivity issues.

Common Symptoms

  • HVAC not turning on when thermostat calls for heat/cool
  • Temperature not reaching setpoint
  • Thermostat showing offline in app
  • Short cycling (system turns on/off frequently)
  • Incorrect temperature readings
  • Schedule not following programmed times

System Not Responding

1. Check Power

  • Verify thermostat display is on
  • Check for any error codes on display
  • Confirm C-wire is connected (required for consistent power)
  • If using PEK (Power Extender Kit), verify installation

2. Verify HVAC Equipment

  • Check circuit breaker for HVAC system
  • Verify furnace door/panel is fully closed
  • Look for blinking lights on furnace control board
  • Check that outdoor unit (AC/heat pump) has power

3. Check Mode Settings

  1. On thermostat, go to Main Menu > System
  2. Verify System Mode is set to Heat, Cool, or Auto
  3. Ensure temperature setpoint is appropriate
  4. Check that system isn't on Hold

Temperature Issues

Not Reaching Setpoint

  • Allow 10-15 minutes for system to affect temperature
  • Check HVAC equipment is sized correctly for home
  • Verify thermostat isn't in direct sunlight or near heat source
  • Inspect HVAC filter—dirty filter reduces efficiency

Inaccurate Temperature Reading

  • Thermostat may need time to calibrate after installation
  • Move thermostat if near heat sources (electronics, sunlight)
  • Use room sensor if thermostat location isn't ideal
  • Compare with separate thermometer to verify accuracy

WiFi Connectivity

Reconnecting to WiFi

  1. On thermostat, go to Main Menu > Settings > WiFi
  2. Select your network and enter password
  3. Wait for connection confirmation
  4. Verify in ecobee app that thermostat is online

Connection Drops

  • Check WiFi signal strength at thermostat location
  • Thermostat needs 2.4GHz network
  • Assign static IP in router if DHCP causing issues
  • Update router firmware

Schedule Issues

Not Following Schedule

  1. Check if schedule is enabled in ecobee app
  2. Verify time zone is correct in settings
  3. Look for manual holds overriding schedule
  4. Disable vacation mode if active

Smart Home/Away Not Working

  • Ensure feature is enabled in settings
  • Motion sensor detects occupancy—may take time to learn
  • Disable if causing unexpected setbacks

Error Codes

Common ecobee error messages:

  • Auxiliary Heat Lockout: Outdoor temp above threshold; aux heat disabled
  • Cooling Disabled: Check outdoor unit and circuit breaker
  • Calibrating: Normal during startup; wait 5-10 minutes
  • No WiFi: Reconnect following steps above

HVAC Compatibility

Verify your system is compatible:

  • Works with most 24V systems (gas, electric, oil, heat pump)
  • Doesn't support 110V/240V line voltage systems
  • Dual fuel systems may need accessory
  • Use ecobee compatibility checker online

Factory Reset

  1. Go to Main Menu > Settings > Reset
  2. Select Reset All Settings
  3. Thermostat will restart
  4. Re-run initial setup and WiFi configuration

When to Contact Support

Contact ecobee support or HVAC technician if:

  • HVAC equipment won't respond at all
  • Burning smell from HVAC system
  • Continuous error codes after troubleshooting
  • Short cycling that could damage equipment