Honeywell thermostats are one of the most popular thermostat models in the market today. These thermostats come with a “Cool On” indicator that indicates the status of the device. However, some users reported that their Honeywell thermostat keeps on blinking, and they are not able to set the desired temperature.

If the same Honeywell thermostat cool on blinking issue is occurring with you as well, and you are looking for a quick fix, then I am here to help you out.

However, if you just started to notice this weird error, then don’t panic right away. The message usually flashes for about five minutes and then turns solid to indicate the system status.

But if it continues to flash, then you can try out the below fixes:

Also Read – Honeywell Thermostat Flashing Heat On? Here’s How to Fix It

What does the Honeywell thermostat “cool on” indicator mean?

honeywell thermostat

If your Honeywell thermostat displays a “Cool On” message, it simply means that the device is in operation mode. When the cooling message appears, it means your AC unit is at work and filling your home with cool air.

Similarly, if you get to see a “Heat On” message, it means your thermostat is making sure your home is getting hot or reaching your desired temperature.

However, If your Honeywell thermostat flashes a cool-on message for a longer period of time, then it could mean that the thermostat is not able to cool down your home, and it requires your intervention.

Is A Thermostat Blinking “Cool On” A Serious Problem?

If you see the “Cool On” or “Heat On” message on your Honeywell thermostat, there is nothing to worry about in most cases.

It is normal for the thermostat to adjust the room temperature to your desired degrees. Also, if you see the message, it only indicates that the thermostat is functioning properly.

In case the cool on message is blinking, then again, you don’t have to panic. Instead, it is just a regular system check. The blinking should get resolved on its own within a few minutes.

You should only worry and look for a fix if your thermostat flashing a cool on message for about 30 minutes or so.

Compressor Protection Feature:

In some newer thermostat models, you now get a compressor protection feature. So, in case your thermostat displays a “Waiting for equipment” message. Then, it simply means your thermostat is using the protection feature.

It is an internal safety feature that safeguards the compressor in case of power outrage. However, it will get fixed on its within 5 minutes or so. Once it is done performing a restart, everything should work just fine.

Also Read – How to Fix a Honeywell Thermostat Fan Won’t Turn Off

How to Fix Honeywell Thermostat Cool on Blinking Error?

1. Wait For 10 Minutes

Before you decide to fix the Honeywell thermostat cool-on flashing error, you must wait for about 5 to 10 minutes. As there is a good chance that your thermostat is going through a restart or running some checks.

Or it might be facing a slight delay or using the compressor protection feature. So wait for a few minutes and see if it gets fixed on its own. If it doesn’t work, then move to the below solutions.

2. Set the temperature to the lowest possible

The next thing you should do is set the temperature to the lowest possible. Make sure to set the mode to Cool and the fan setting to “Auto”. And then check if your thermostat is able to regulate the temperature or not.

Keep the settings in this way for a few minutes and see if you can see any noticeable changes in the room temperature. If it’s cooling your room down, then set the settings back to what it was and let the thermostat run normally.

3. Check if the Thermostat is in Setup Mode or if the Clock is Set

In specific models, when the thermostat recovers from a power outage, it may get back to the setup mode. As a result, it will flash cool on lights.

To resolve this, you must redo the thermostat settings and make all the necessary changes. Also, you must verify the time displayed on your thermostat and make sure it is accurate. As an incorrect setting can interfere with your scheduled settings. 

Also Read – How to Set Honeywell Thermostat Temperature? (Heat and Cool)

4. Don’t ignore the batteries

Cool on blinking Honeywell thermostat error could also appear because of drained-out batteries. As batteries are needed for the thermostat to operate effectively. So if the batteries are dying or don’t have enough juice left, then it is obvious to face various issues.

To make sure that batteries aren’t the culprit, look for the battery low indicator message on your thermostat display. Even if you don’t see any message, try replacing the batteries and see if it resolves the issue for you.

5. Make sure your AC unit has power

The issue could be with your AC unit and not with the thermostat. So make sure to check your AC unit and see if it has power.

Just head over to your indoor and outdoor units and check if they are properly powered up. You can also go through the connections, sockets, and power supplies and ensure that everything is in place.

6. Check air filter

If your AC unit has a dirty or clogged air filter, then it can prevent proper cooling in your home. Even force the thermostat to act weird. To ensure that this is not the case, check the air filter and change it from time to time (usually in every 3 months).

7. Examine AC coils

Apart from dirty air filters, the issue could also occur because of dirty AC coils. Over a period of time, the AC coils can attract a lot of dirt, which can restrict airflow. As a result, your Thermostat may not work properly, leading to various other issues. So make sure to check on the AC coils and see if they are dirty or clogged. You should also clean off the dirt and then check if you are still experiencing the same Honeywell thermostat blinking cool on error.

8. Bypass Honeywell thermostat

Another fix that you can try out is bypassing the Honeywell thermostat. However, it requires expert technical skills, and you should only do it if you are skilled enough to deal with electrical components and have multi-metere and proper tools to create a jump wire.

If you find yourself fit for the job, follow these steps:

  • Begin by turning off the power switch on the furnace or air handler, and ensure the thermostat is disconnected from the breaker as well.
  • Next, remove the thermostat from its wall mount.
  • Subsequently, connect one end of a jumper to the R (Power) terminal and the opposite end to either the Y (Cooling) or W (Heating) terminal on the thermostat contacts.
  • Once this configuration is established, reinstate the power and assess whether the AC unit or furnace/air handler initiates operation.

9. Reset the Thermostat

In case none of the above methods worked out for you, then resetting the Thermostat can be a solution. Just like any other device, a simple restart often fixes the major issues. As it will wipe out all the settings and programming. So before you reset, make sure to take note of the settings. After resetting your Thermostat, set it up again and see if it works out for you.

Also Read – If you have a Vivint Thermostat that you want to reset, click on this link.

To reset the Thermostat, follow these steps:

  • First, power off your Thermostat and remove the batteries.
  • Then, put in the batteries in the wrong way – with negative to positive and positive to negative.
  • After that, wait for about 10 seconds or so.
  • Remove and put in the batteries in the correct way.
  • That’s it; your Thermostat will be set to factory settings.

To help you out, here is a video that you can check out:

10. Get professional help

If, in the end, nothing works out for you, then you must get professional help. A trained technician will be able to find out the real cause by checking various things such as wire connections, thermostat voltage, etc, and help you with a fix. Also, if anything needs to be replaced, they will be able to do so.

Why is the cool button on my Honeywell thermostat blinking?

Check for cooling on the thermostat display, which is commonly represented by the words “cool on” or a snowflake icon. If these icons flash, it means that the thermostat is in delay mode, which can last up to 5 minutes. This delay prevents your equipment from cycling too quickly.

How do you reset a thermostat manually?

Installing the battery backward for five seconds, pushing a recessed reset button with a pin or paper clip, or turning off the thermostat’s breaker for 30 seconds are all common techniques for resetting a thermostat.

How do you know if your thermostat is clogged?

You have to wait till the engine warms up. After 10 to 20 minutes, the coolant should attain the proper temperature and begin to flow. If it does not begin to flow, but the temperature indicator on your dashboard rises, this indicates that your thermostat is stuck closed.


So that was all for how to fix the Honeywell thermostat cool on blinking error. By following the above steps, you should be able to troubleshoot the cause of your flashing “Cool On” thermostat and get your air conditioning system running properly again. If none of the mentioned tips doesn’t work, then you must contact the customer care center.

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