Lennox ComfortSense L5711U

Questions and Answers

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Nathaniel MartinAug 19, 2025
What to do if Lennox ComfortSense L5711U Thermostat heating system does not turn on?
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  Derek GordonAug 19, 2025
  If your Lennox thermostat's heating system isn't turning on, try these steps: * Ensure the SYSTEM key is set to heat. * Verify the heat temperature setting is above the room temperature and "Heat On" is displayed. * Check the circuit breaker and the power switch for the heating/cooling system. * Confirm the furnace door is securely closed. Allow five minutes for the heating system to respond. If the issue persists, consider contacting a qualified service technician.
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Frank JonesAug 21, 2025
What to do if Lennox ComfortSense L5711U cooling system does not turn on?
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  rhonda08Aug 21, 2025
  If the cooling system on your Lennox thermostat isn't turning on: * Press the SYSTEM key to set it to Cool. * Make sure the cooling temperature is set below the room temperature, and "Cool On" is displayed. * Check the circuit breaker and the power switch for the heating/cooling system. * Ensure the furnace door is securely closed. Allow five minutes for the cooling system to respond. If the problem continues, contact a qualified service technician.
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Victoria MorganAug 23, 2025
How to fix Lennox ComfortSense L5711U Thermostat when "Heat On" is not displayed?
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  groblesAug 25, 2025
  To fix this, set the System setting to Heat and ensure the temperature setting is above the current room temperature. If "Heat On" appears but the heating system still doesn't turn on, refer to the suggestions for 'Heating system does not turn on'.
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Steven EvansAug 26, 2025
What to do when "Cool On" is not displayed on Lennox Thermostat screen?
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  Nicholas HernandezAug 26, 2025
  To resolve this, set the System setting to Cool and make sure the temperature setting is below the room temperature. If "Cool On" is displayed but the cooling system doesn't activate, see the troubleshooting steps for 'Cooling system does not turn on'.
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Rachael WrightAug 28, 2025
What does "Wait" mean on my Lennox Thermostat?
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  Christina TorresAug 28, 2025
  The message "Wait" indicates that the compressor minimum-off timer is active. Allow up to five minutes for the compressor to turn on.
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Edward GomezAug 30, 2025
How to fix blank display on Lennox ComfortSense L5711U Thermostat?
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  daniel45Aug 30, 2025
  Ensure that fresh AAA alkaline batteries are correctly installed in the thermostat, following the markings inside.
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Tonya TaylorSep 1, 2025
Why temperature settings do not change on Lennox ComfortSense L5711U Thermostat?
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  Michael GarrisonSep 1, 2025
  Make sure your temperature settings are within these ranges: * Heating: 40°F to 90°F (4.5°C to 32°C). * Cooling: 50°F to 99°F (10°C to 37°C).
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Mrs. Danielle KingSep 4, 2025
Why is my Lennox ComfortSense L5711U Thermostat heating in Cool mode?
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  Karen WilliamsSep 4, 2025
  Check Installer Set?Up Number 170: Heating and/or Cooling Type*. Make sure the setting matches the installed heating and/or cooling system.
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Thomas SimmonsSep 6, 2025
What to do if Lennox Thermostat heating system does not turn off?
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  Leonard BaileySep 6, 2025
  Check Installer Set?Up Number 170: Heating and/or Cooling Type*. Make sure the setting matches the installed heating and/or cooling system.
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Nicholas MooreSep 8, 2025
Why are Lennox ComfortSense L5711U Thermostat heating and cooling systems running simultaneously?
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  Christopher WallsSep 9, 2025
  Verify Installer Set?Up Number 170: Heating and/or Cooling Type*. Ensure it accurately reflects your installed system. Also, check that bare wire portions aren't touching each other.

Summary

Thermostat Features

Clear Backlit Display

Large, clear display with backlight shows current temperature, setting, and time even in dark.

Menu-Driven Programming

Menu-driven programming makes set-up effortless via touch screen interaction.

Real-Time Clock & Auto DST

Real-time clock maintains time during power failures and auto-converts to daylight savings time.

Saving Changes Notification

"Saving Changes" notification assures users that changes have been saved correctly.

Reminder Notifications

Reminders notify users of needed maintenance like filter, UV lamp, or battery replacement.

Thermostat Display

System Settings

Fan Settings

Program Your Heating and Cooling Schedule

Schedule Periods Defined

Defines four daily schedule periods: Wake, Leave, Return, and Sleep for comfort and energy saving.

Fan Schedule

Fan Setting Options

Details ON (continuous), AUTO (system on), and CIRC (random) fan operation modes.

Cancel a Schedule Period

Set the Time

Override Temperature Setting-Temporary Hold

Override Temperature Setting-Permanent Hold

Override Temperature Setting-Vacation Hold

Temperature Recovery Feature

Clean the Thermostat Screen

Battery Replacement

Reminder Timers

Resetting Timers

Instructions on how to reset reminder timers for filter, humidifier, or UV lamp after replacement.

View Timer Settings

How to view and modify timer settings and reload values before they expire.

Built-In Compressor Protection

Outdoor Temperature

Advanced Heat Pump Features

Screen Lock

Partially Locked Screen

Locks most keys but allows temperature adjustment; temporary changes last until next schedule.

Fully Locked Screen

Locks all keys except access to user set-up options via SYSTEM key.

Advanced Settings

Troubleshooting Tips

Lennox ComfortSense L5711U Specifications

General

Category	Thermostat
Model	ComfortSense L5711U
Display Type	Touchscreen
Wi-Fi Connectivity	Yes
Power Source	24V AC
Temperature Range	40°F to 99°F
Humidity Control	Yes
Scheduling	7-day programmable
Backup Battery	No
Type	Smart
Compatibility	Works with most HVAC systems
Stages	2 heat / 2 cool
Warranty	5 years