Honeywell Thermostat Cool on Blinking: How To Fix?

A malfunction with both the air conditioning system is the worst-case scenario on a sweltering summer day. It’s not the end of civilization if you run into difficulty, however. My air conditioner has never given me any problems, but my Thermostat just malfunctioned for the first time.

‘Cool On’ began flashing, however, there was no cool air flowing out of another HVAC system after just a few minutes.

Even though I didn’t realize it, the system had been attempting to warn me something wasn’t quite right. As a result, I began by investigating the potential causes of the flashing problem before making a list of all the possible solutions. If the ‘Cool On’ indicator on your thermostats is also flashing, you’ve come to the right place.

If your Honeywell Thermostat After 5 to 6 minutes with a ‘Cool On’ sign blinking, lower the Thermostat and see whether it’s in setup mode. Make sure the Ventilation systems components have electricity by checking the batteries. Replace the air conditioner’s filter and coils if necessary. Please restart your Thermostat if none of these solutions work for you.

Honeywell Home RTH221B1039 1-Week Programmable Thermostat
  • ONE WEEK PROGRAMMING: Set one identical program for the entire week with four program periods per day including wake, leave, arrive and sleep.
  • PRECISE TEMPERATURE CONTROL: Precise temperature control of plus/- 1 degree Fahrenheit
  • DIGITAL DISPLAY: Easy-to-read digital display with an intuitive interface for one-touch access to setpoint temperature
  • EASY INSTALLATION: Easy to install yourself and basic operation keeps programming simple
  • REMINDERS: Built-in battery change reminders (2 AAA batteries are required for operation)

Demystifying the ‘Cool On’ Indicator

Whenever you see the ‘Coon On’ sign flashing, don’t be alarmed. Essentially, this signal is a way of functioning that lets you know about something. There is an indication in the system unit, similar to ‘Heat on’ mode, indicating operations have begun in that unit.

The cool on the light will return to normal after a few minutes (let’s say 5). This means there is no need to be concerned if it flashes briefly. This mode kicks in to protect the HVAC system’s compressor from harm. It may also happen if the device loses power.

How to Identify Something is Wrong?

So, what’s the big deal here? Fixing the ‘Cool On’ light is pointless if it’s just there as a safety precaution. When the ‘Cool On’ indication has been flashing for more than five min, and no cool air is flowing out of another HVAC system, you have a problem.

This raises a red signal that must be addressed. The actions listed below will help you figure out why your ‘Cool on’ indication keeps blinking.

Change the Temperature to The Lowest Possible

To begin, check to see whether the Thermostat is capable of controlling the temperature. Check to check whether the cooling works by adjusting the controller settings. While still in ‘Cool’ mode and with the fan set to ‘Auto,’ lower the temperature as much as possible on your computer.

Check whether there has been any cooling or visible change in the room’s temperature after doing this for a while.

Check if Thermostat Is in Setup Mode or the Clock Isn’t Set After Blackout

A power loss or a blackout may also force the Thermostat into setup mode, causing the ‘Cool on’ light to begin flashing. Check and see whether the temperature is on or off since it might produce this flashing signal. If this is the case, go through the settings and make any necessary adjustments.

Check the batteries 

The Thermostat won’t work properly if the batteries are depleted. It’s time to change the batteries if they’re weak. There are 60 days of battery life left when the Thermostat shows a low battery level on display. The Thermostat’s display lets you keep an eye on the charge level of your batteries.

If your Thermostat is not battery-operated, it runs on 24 VAC and requires wiring inspection. The first step in inspecting the wiring is to turn the system off and remove the plate.

This is how you can verify the C-wire is working properly. You may have to remove the Thermostat from the plate by unscrewing it. After changing the batteries, it’s conceivable that your Honeywell Thermometer Display Backlight may no longer operate.

Reset Honeywell Thermostat.

Check if Your HVAC System Components Have Power

Because you’ve done everything up to this point and it’s not working, you’ll have to exercise greater patience in the future. It’s time to make sure everything in the HVAC system is in functioning order.

Look for clicking or buzzing sounds that suggest a problem with the computer’s hardware. Verify that all equipment, such as the furnace, air handler, and air conditioner, has electricity. To check if sockets and supplies are correctly connected, turn on all of the switches.

Check to see whether the unit’s doors are closed correctly and if anything is loose inside. Check to see if anything is preventing the device from working properly.

As a last check, ensure sure the circuit breakers are working properly. Before doing any more troubleshooting, make sure all electrical outlets are closed. After switching off, a voltmeter may be used to check for blown fuses. 

Check if the AC filter Needs Replacing

It does not matter because all of your HVAC components, including the system unit, are operating properly; if your AC filter is clogged, your cooling will suffer. The Thermostat, air quality, and electricity bill all suffer from poor AC filter performance.

Change the air conditioner’s filter every three months to keep it from becoming clogged with dust and grime and reduce the cooling efficiency. It takes longer for the air conditioner to cool because a filter is blocked, which puts additional strain on the compressors and other components.

If this happens, expect a significant decrease in temperature and problems with certain other HVAC components. This is because the indoor coil is partly frozen, or the registers are blocked.

Check if the AC Coils are Dirty

Like the filter, the AC coils accumulate dirt as well. The exterior AC coils on your HVAC system may be clogged or unclean. The air conditioning coil does not need to be cleaned regularly. It collects dust for months or even years before it becomes blocked and no longer allows ventilation.

The coil will not absorb the heat in this situation, which will reduce overall cooling. To prevent the AC coils from being clogged with debris, you must first determine whether they need cleaning.

It is necessary to turn off the machine and clean the floor surrounding it before cleaning the coils. This will help prevent the coils from becoming clogged in the future. Make sure the equipment is in a wide space with no vegetation or equipment in the way to enhance ventilation.

Reset Your Honeywell Thermostat

It’s time to restore your Honeywell Thermostat’s factory default settings once you’ve double-checked everything on the device. This will reset the device to its factory settings and delete any previously stored data. If you wish to keep the initial configuration, make a note of it.

Before doing a factory reset on the Honeywell thermostat, make sure you know its model number. It is necessary to unplug the Thermostat if C-wire powers it. For a few seconds, press and hold your Thermostat’s Menu button to reset it. You’ll be able to return to your old settings after performing a reset on the device.

Honeywell WiFi Thermostat Connection Problems

Check the User Manual 

To be on the safe side, make sure you read the user handbook thoroughly. It contains valuable information on a wide range of possible problems. All of the instructions are specific to your thermostat model, which means they are the most accurate.

If you want to learn more about frequent issues and bugs, see the handbook. You may also get the user manual from the internet if you misplace it.

Call Honeywell Tech Support

If you’ve followed the above procedures to a tee and nothing has worked, give Honeywell Tech Support a call. It’s simple for a tech expert to identify the problem and solve it right away. Defective cabling, damaged plugs, blocked sensors, and defective capacitors may all be repaired by a skilled expert.

The professional will also inspect the air compressor, compressor, and condenser, if necessary. The technician Your problem will be solved, and your Thermostat will be correctly adjusted to your system thanks to the expertise of Honeywell Tech Support.


Now you know how it was that your Honeywell Thermostat says “Cool On” even if no cool air is blowing from it, and you can take the required measures to correct it.

The Honeywell thermostat gives you complete control over your HVAC system’s humidity levels. It also has a variety of useful functions, including zone management, oxygen diffusion regulation, internal humidity sensor, and more.

Best Seller List of Honeywell Thermostats:

SaleBestseller No. 1
Honeywell Home RTH9585WF Wi-Fi Smart Color Thermostat, 7 Day Programmable, Touch Screen, Energy...
  • COMFORT COMES IN YOUR COLOR. Personalize your Wi-Fi Smart Color Programmable Thermostat to fit your décor.
  • SAVE ENERGY AND GET REWARDED by checking with your energy provider about available rebates. Plus, eligible customers can enroll in their local Utility's "DEMAND RESPONSE PROGRAM" which can reward you for allowing the utility to slightly adjust your AC or furnace temperature settings when there is high energy demand.
  • YOUR SCHEDULE. YOUR WAY. Flexible programming options for your schedule or utility company’s peak rate pricing.
  • EASY OPERATION AND INTUITIVE. Bright, easy-to-read touchscreen makes for simple operation.
  • COMPATIBLE WITH: Forced air (gas, oil or electric), hot water and steam, and heat pumps with electric backup. Does NOT work with electric baseboard heat (120-240V). C-Wire required.
SaleBestseller No. 2
Honeywell Home RTH2300B 5-2 Day Programmable Thermostat
  • 5-2 DAY PROGRAMMING: Separate programs for the weekdays and weekends with 4 program periods per day including wake, leave, arrive and sleep
  • PRECISE TEMPERATURE CONTROL: Precise temperature control of plus/- 1 degree Fahrenheit. Temperature range limits allow you to set minimum cooling and maximum heating temperatures
  • DIGITAL DISPLAY: The display panel is backlit with an intuitive interface for one-touch access to setpoint temperature
  • EASY INSTALLATION: Easy to install yourself and works with many heating/cooling systems, plus heat pumps without auxiliary heat
  • REMINDERS: Built-in battery change and filter change reminders
SaleBestseller No. 3
Honeywell TH4110U2005/U T4 Pro Program Mable Thermostat, White
  • Country Of Origin: United States
  • Model Number: TH4110U2005/U
  • Item Package Dimension: 6.49999999337" L x 5.099999994798" W x 2.299999997654" H
  • Item Package Weight: 13.8 oz
SaleBestseller No. 4
Honeywell Home RTH7600D 7-Day Programmable Touchscreen Thermostat
  • Large touchscreen display makes it easy to set your preferred temperature or set a weekly schedule for automated adjustments.
  • Set home and away temperatures to help save energy when you're not home. Temporary and permanent hold settings are also available for extended absences from home.
  • 7-Day menu-driven programming with 4 periods per day.
  • Backlit touchscreen display shows current room temperature and set point temperature simultaneously.
  • Simple and straight forward to install and use. The thermostat also has a real-time clock so it will automatically adjust for Daylight Savings Time.
SaleBestseller No. 5
2,989 Reviews
Honeywell Home RTH8560D 7 Day Programmable Touchscreen Thermostat White
  • Scheduling your heating/cooling cycles to fit your lifestyle is easy to do, with options to program day-to-day, over the weekend, or for an entire week..Includes : Package includes thermostat and receiver | Thermostat Type : Programmable
  • The crystal-clear display on the T5 Touchscreen Thermostat provides a seamless blend of function and style.
  • The screen is brightly backlit with a cool blue color and provides an easy-to-read indoor temperature, including indoor humidity readouts.
  • For added convenience, reminders to change air filters appear on the screen.
  • The advanced design of this thermostat provides maximum comfort by sensing whether your home needs heating or cooling with the Smart Response Learning technology.
SaleBestseller No. 6
Honeywell TH6220WF2006/U Lyric T6 Pro Wi-Fi Programmable Thermostat with Stages Up to 2 Heat/1 Cool...
  • 4-1/16 in. Long x 4-1/16 in. Wide x 1-3/32 in. Deep
  • 20 to 30 vac
  • 37 f to 102 f
  • 4-1/16 in. Long x 4-1/16 in. Wide x 1-3/32 in. Deep
  • 20 to 30 vac
SaleBestseller No. 7
Honeywell Home RTH6580WF Wi-Fi 7-Day Programmable Thermostat
  • ENERGY STAR certified. Help save energy, track your heating and cooling with monthly energy reports and get personalized tips on reducing energy use.
  • SAVE ENERGY AND GET REWARDED by checking with your energy provider about available energy savings rebates to save on your purchase (rebate finder link above). Plus, eligible customers can enroll in their local Utility's "DEMAND RESPONSE PROGRAM" which can reward you for allowing the utility to slightly adjust your AC or furnace temperature settings when there is high energy demand.
  • C-WIRE POWER ADAPTER REQUIRED: Before purchasing, check to see if this thermostat is compatible with your home and to determine if your home needs a C-wire power adapter.
  • SMART HOME INTEGRATION. The Wi-Fi 7-Day is compatible with voice assistant devices like Amazon Alexa, Google Assistant, Microsoft Cortana, and more.
  • THERMOSTAT THAT FITS YOUR LIFE. 7-day, 4 periods per day, flexible programming lets you sync your comfort with your schedule.
SaleBestseller No. 8
Honeywell TH9320WF5003 Wi-Fi 9000 Color Touch Screen Programmable Thermostat, 3.5 x 4.5 Inch, White,...
  • Made in United States
  • Package length : 6.0"
  • Package width : 2.0"
  • Package height : 8.0"
  • Material Type: Plastic
Bestseller No. 9
25 Reviews
Honeywell TH3110D1008 Pro Non-Programmable Digital Thermostat, 1 Pack, with Playhardest Cleaning...
  • Bundle Includes: Honeywell Home TH3110D1008 PRO 3000 Non-Programmable Digital Thermostat & Playhardest Cleaning Cloth
  • Displays both room temperature and temperature setting
  • One-touch temperature controls
  • Large, clear backlit display is easy to read, even in the dark
  • Switchable fan control (auto or continuous fan)
Bestseller No. 10
Honeywell TH8321WF1001 Touchscreen Thermostat WiFi Vision Pro 8000 with Stages Upto 3 Heat / 2 Cool
  • With a large touchscreen display, the VisionPRO 8000 WiFi Programmable Thermostat makes it easy to control your home comfort.
  • Program a schedule for every day of the week or control the temperature remotely anytime from the Total Connect Comfort app.
  • Adaptive Intelligent Recovery
  • Schedule for Energy Savings
  • Set the same schedule each day, adjust it on weekends, or customize it by the day.



1. Why is my Honeywell thermostat not working?

Many factors might lead to a Honeywell Thermostat not operating properly.
The HVAC accessibility door may not be closed correctly, the batteries may be dead, or the circuit breaker may have tripped, all of which might result in a problem.

2. How do I manually override my Honeywell Thermostat?

To manually override your Honeywell thermostat, press and maintain the display button and swiftly hit the up arrow button while still holding it down. To switch to manual mode, release all of the Thermostat’s buttons.

3. What is the recovery mode on the Honeywell thermostat?

When the Panasonic thermostat is in recovery mode, the device is trying to maintain a temperature that is different from the surrounding area. It simply implies it has just exited electricity mode and is beginning the process of recuperating.

4. How do I bypass the recovery mode on a Honeywell thermostat?

Honeywell’s recovery mode may be bypassed by turning it off in the system preferences. You may restart it at any moment after you disable it. Alternatively, if you want to prevent it temporarily rather than completely, you may set a timer.

5. How do I set my Honeywell thermostat to permanent hold?

Press the + or – button on your Honeywell Thermostat and then adjust the temperature. Temporary hold and a blinking setpoint temperature are shown on the Thermostat. Hold the ‘hold’ button-down, although the thermometer is flashing to make it permanent.

-our editorial board has reviewed this article and has been approved for publication according to our editorial policy.

Last update on 2024-04-08

Lance Ulanoff is a renowned tech journalist, commentator, and on-air expert with over 36 years of experience. He has held esteemed positions including Editor in Chief of Lifewire and Mashable, where he delved into the impact of technology on daily life. Lance's expertise has been featured on major news programs globally, and he has made appearances on Fox News, CNBC, and the BBC.