Smart HomeThermostatHoneywell Thermostat Blinking Cool On?- 7 Things to Fix

Honeywell Thermostat Blinking Cool On?- 7 Things to Fix

After a long day, everything I expect is to relax in my chilled Keeping room doing my favorite task. Recently I had to face the issue of the Honeywell thermostat blinking “cool on” for a few minutes but AC is not working.

Ugh! Well, it is natural to be concerned if you find your Honeywell thermostat flashing cool on. However, you don’t need to be flustered as your thermostat is not damaged. We will guide you with a few rules and contribute to solving your problem. So be hassle-free!

As the demand for thermostat devices keeps increasing, Honeywell thermostat flashing cool on is one of the common issues people are facing. We will look into the reasons why this problem occurs, and what you should do about it.

What is the “Cool On” Indicator In Honeywell Thermostat?

Before that, what does this cool on indicator means? A thermostat usually has 3 modes, heat, cool, and off. When the Cool On signal is selected, the compressor and the indoor fan turn on and cool air blows out of the system.

If you find the Honeywell Thermostat flashing “Cool On”. It signifies two things: first, the AC system is kickstarting. This will take approximately around 10 minutes giving time to cycle its elements and is absolutely normal.

Second, if there’s something serious and you need to check it out ASAP!

Why Is Honeywell Thermostat Blinking Cool On?

The Cool On indicator should be stable. It shouldn’t be blinking or flashing. However, if you find the Honeywell thermostat blinking Cool On, then there are possibilities of technical malfunctions.

Power Outage: When your power goes out or if there are any interruptions in the power, then you hope that all devices will work perfectly when the lights turn on. Like other devices, the compressor of the thermostat is forced to restart which puts build pressures. This might lead to the Honeywell thermostat flashing Cool On. This is one of the common and most found reasons people deal with.

The compressor will start again in a small time period: In case you manually readjust the temperature of your thermostat after the HVAC system has reached the set temperature, it will force the compressor to restart again.

Changing the heating, cooling or vice versa. When you do this the thermostat display will blink due to the additional pressure on the compressor.

Battery replacement: In case, if you just replaced the batteries, wait for a little longer. The cool on display must flash soon.

A low battery: Sometimes the thermostat tries to reach out to you and tell you that you’re running on a low battery by flashing cool on. While some thermostats display notifications and adapt to a modern system. The others still continue flash signals.

There are several solutions to solve such problems. We will list the solutions in 7 easy steps that you can follow to fix your thermostat and get on with your work.

How To Fix If Your Honeywell Thermostat Flashing Cool on?

Before doing anything to your thermostat, just give it time to finish the timeout feature of the Honeywell thermostat. So that compressor does not get damaged due to differences in pressure created by the compressor.

Still, the Honeywell thermostat is flashing Cool On after waiting of long period of more than 10 minutes, Try the following method to fix it.

1. Set the Thermostat Setting to the Lowest Temperature.

Here you have to check whether the thermostat can control and handle the cooling. Use the controller and try to adjust the cooling to see if everything is working smoothly and if the remote works fine. Set the controller to the minimum temperature and ensure that you are on the cool mode in the setting.

Also, ensure that your fan setting is on Auto mode. Be patient for some time and notice if there are any changes or differences in the temperature.

2. Set the Clock, Check if the Thermostat Is in Setup Mode

Power outage or any interruptions in the power cause the thermostat to automatically switch to the setup mode. This is also one of the reasons why you find your Honeywell thermostat flashing cool on. Keep an eye on the clock and review all the settings accordingly.

3. Check Whether the Batteries Are Working

Batteries aren’t forever. Battery issues are always on the horizon. If the batteries are spoilt or may be leaking, the thermostat will not initiate cooling or heating mode. Change the batteries and check if there is any difference. The thermostat normally displays the battery low indicator. It gives you a buffer of 2 months to change your battery.

4. Examine the Fans, Furnaces, and AC units.

If you have checked your batteries and still the blinking hasn’t stopped. It is necessary to now have patience and inspect your units. However, this is a crucial process. If you hear any unusual sounds like humming or clicking noises, then immediately take your hands off and call the professional.

Otherwise, check the equipment and examine if all the units are receiving the amount of power they need to function. Turn the equipment on and off with utmost care. After checking, plug the wires properly and turn on the switches. Check and review the settings accordingly.

5. Look Over the AC Filter and Coils

The AC filter greatly affects the cooling of the AC system. If there are any issues with the filter, then you will notice less cooling or similar issues. It also affects your power bill. Every AC filtered is recommended to be changed after every 3 to 4 months, which if not done will create issues.

The dirt gets clogged and it’s most likely to stop working in another month. If you do not remember the last time you replaced or cleaned your AC filter, now is the time to do so. Also keep the coils collecting dirt after years of usage, because of which there are possibilities that the Honeywell thermostat is flashing cool on.

6. Reset Thermostat Device

If all the above things have ticked on the list but there is no change, then resetting the thermostat might help. Before doing so, remember to note down all the configurations. Reset the device to factory default. Depending on the Honeywell model, you can reset it. Use the instructions manual for the same. After resting, set your device and make changes as required.

7. Check the Instruction Manual or Call the Pro

Tried everything but still, nothing changed? Let’s give it another shot! Try reading the user manual. Check all possible ways. No Idea? Then it’s safer to call the professional now. They can fix all problems including damaged wiring or if there are any other issues in the sensor or fuse.


Every problem does have a solution. Usually, the Cool On indicator flashing can easily be resolved in a few steps. They are less likely to need professional help. It’s always good to try what you can, might help save some money too. However to be on the safer side, once you have tried all the above-mentioned steps, you will have to rely on professional help only. There are chances of complex issues like excessive defrosting or overheating blowers.

We hope this article has explained to you why your Honeywell thermostat flashing Cool On and what you can do to fix it. Wait we are also actively looking for professionals to write for us home improvement guest posts to contribute to our blog.

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