Honeywell Thermostat Blinking Cool On? – Methods To Get It Fixed

You shouldn’t be concerned if you notice the “cool on” light flashing or blinking on your Honeywell thermostat. Usually, this indicates that the air conditioning unit is getting started.

After a few minutes, the light should turn off when the AC starts working properly. 

If the light doesn’t turn off after 5 minutes, there may be a bigger problem. Without the manual, fixing the Honeywell thermostat flashing or blinking cool on issue can be confusing.

To troubleshoot your Honeywell thermostat flashing or blinking cool on issue, we’ll guide you through a couple of steps.


Here is a quick guide on how to fix the Honeywell thermostat flashing “Cool On” error.

Would you like to know if you are affected by the Honeywell thermostat cool on blinking problem? If this is the case, you are not alone, and this is a common problem that occurs with air conditioning systems. It can be a hassle to deal with this problem, but there are a few troubleshooting tips that can resolve it quickly.

Here are some tips and steps to assist you fix the cool on a flashing Honeywell thermostat.


What could be the reason for my Honeywell thermostat flashing “cool on”?

Now that we’ve talked about how to fix a Honeywell thermostat that’s constantly blinking or flashing “cool on”, let’s talk about how it works. Your thermostat controls the “cool on” light as one of its operation modes.

The “cool on” setting is similar to the “heat on” setting, but only indicates that your home is being cooled.

Short periods of blinking or flashing “cool on” are normal on a Honeywell thermostat. Your thermostat may not be malfunctioning if this happens. To safeguard the compressor, the thermostat comes with this safety feature.

By using the “cool on” feature, the system will work through its elements and do its job effectively. In addition to this, there is also a risk that it will flash in the event of a power outage.


Is there a way to troubleshoot Honeywell thermostats that flash the “cool on” light?

There doesn’t even appear to be any cool air coming through your system at all? Has the “cool on” light been flashing for longer than five minutes? If this is the case, then we have a few solutions you can try that will hopefully help you to resolve the issue.


The thermostat setting should be lowered.

Testing whether your thermostat controls the cooling in your home is one of the easiest fixes. Check to see if the temperature changes after lowering it to the lowest setting for an hour or two. A simple cooling down of the system could solve the problem.

It is imperative that your Honeywell thermostat is set to “cool” mode and that the fan is switched to “auto”. The temperature should be reduced so that it is as low as possible on the thermostat.

If your home’s temperature has changed after it’s been left to work, check to see if anything has happened.


Are you in setup mode on the thermostat or do you have the clock set?

When there has been a power outage, your Honeywell thermostat may flash “cool on” repeatedly. The Honeywell thermostat flashing “cool on” repeatedly after a vacation could be a sign that something has happened.

This means that your thermostat has been switched back to setup mode. You may see the “cool on” light blinking repeatedly if this is happening. It is likely that once you reset your thermostat, this problem will be resolved. 

Make sure the thermostat’s time settings aren’t turned off, or that they don’t show as set. Your Honeywell thermostat may also not be working properly due to this issue.


Weak or Dead Thermostat’s batteries can cause thermostat flashing Cool On.

In some cases, the thermostat won’t work properly if its batteries aren’t powerful enough. When the batteries run out of juice, they won’t be able to heat or cool your house! I’m lucky enough to be able to resolve the Honeywell thermostat flashing cool on issue easily.

You can change the thermostat batteries by removing the old ones.

Make sure the “battery low” light on the display is flashing if it is on. Around two months after your thermostat displays this warning, your power usually starts to fail.

This could be the cause if you noticed a flashing light before you noticed the flickering “cool on” light.

Do you use 24 VAC instead of batteries to power your thermostat? In case the wiring needs to be checked, you should do so. It is very imperative that while doing so, you do not electrocute yourself. Before starting up again, ensure the system has been fully shut down.

If there is no power going to the thermostat, you can detach it from the wall. The wall mount must be unscrewed in order to be removed. 

To ensure everything is functioning correctly, check the C-wire of the thermostat. When you are not sure how to check the wiring, you can ask an electrician for help.


Is power available to the air conditioner, furnace, and air fans?

When the “cool on” light on the Honeywell thermostat is still blinking or flashing after following the above steps, it is imperative to take a deep breath and be as patient as possible. It can be frustrating to try to figure out what went wrong.

If you hear strange humming or clicking noises when checking your Honeywell thermostat, make sure to note them. If this happens, there may be something else wrong.

You should ensure that your thermostat equipment is in good working order at all times. Does everything get the right amount of power it needs to function properly? Make sure all connectors, power supplies, and sockets are in good condition.


Are all the plugs plugged in correctly and are all the switches turned on?

Your Honeywell thermostat equipment should have all components in working order. Are all the doors closing properly? Are there any loose or unscrewed parts? What appears to be blocking or preventing the equipment from performing its duties?

Is there a problem out of the ordinary with the circuit breakers? Restart the equipment by turning it off and on again. Do the same at the circuit breaker as well.

You may need to use a voltmeter to see if any fuses have blown if you still can’t figure out what’s wrong.


Is it time to change the indoor AC filter?

It is possible to throw your whole system out of whack if you do not replace your indoor filter. Whether your Honeywell thermostat equipment works fine or not does not matter!

Air quality and your thermostat can both be affected when your indoor filter needs to be replaced. It can even affect your power bill!

It is recommended that AC filters be changed every three months or so. Your air conditioner’s performance can be affected when its filter becomes dirty or clogged.

Due to the unit’s increased workload, the filter may break down more quickly.

 Your thermostat could also be affected by a dirty filter, resulting in drastic temperature changes. If the thermostat registers are blocked or the indoor coil becomes partially frozen, this can occur.


Do the AC coils need to be cleaned?

AC coils are another component to check. It is important to check if these have become clogged or dirty, just as you would with the filter. It is possible for dirt to build up on the coils after a couple of years.  However, it will be prevented from receiving proper airflow if this happens.

The coil won’t be able to cool the air or absorb heat as well if it is dirty or blocked.

You should be able to tell if the AC coils are the problem based on a look at them. The fins will become dirty as dirt builds up. It’s important to turn off your AC unit before you clean it.

You should clean the surrounding area to prevent your AC from becoming clogged up sooner. The AC unit should also be placed far enough from anything in your home that could interfere with airflow.

This category includes plants and leaves.


Resetting your thermostat to its default settings might fix thermostat flashing Cool On.

The thermostat can be reset back to its original factory settings once you have checked all the other aspects. Make sure you note down the program and preferred settings you have installed before wiping them clean.

Different Honeywell thermostat models require different methods for resetting them. Be sure to power down your thermostat before you do anything if it is powered through the C-wire.

Pressing and holding the menu button for several seconds can reset models with a menu button. You should then see a prompt asking for “reset or factory reset”. If you have a different thermostat model, you may discover this within the “preferences” option.

Following the factory reset of your thermostat, you can select your preferences.


Consult the thermostat’s manual for more information.

The most obvious solution is to check the manual of your thermostat. The information should help you figure out what exactly is wrong if you can’t figure it out. Depending on your Honeywell model, you may even find specific tips.

Do you no longer have your manual? Honeywell’s website or customer service department can help you find the model number of your thermostat if you know it.


Still getting Honeywell Thermostat Blinking Cool On error message, Contact a technical engineer for further assistance.

Despite trying everything, you may not be able to figure out what the problem is. In this case, a professional engineer should be contacted. It could be an easy fix for them if your HVAC system has worked perfectly for you up until now.

A professional engineer can repair damaged or faulty wiring, blown fuses, blocked sensors, or faulty capacitors. Additionally, they can check your HVAC system’s fan motor, condenser, and compressor.

In newer installations, it may just be a matter of making sure the wires are in the right place. The thermostat can also be configured properly by a professional engineer.


Conclusion: Honeywell Thermostat Blinking Cool On.

It is our hope that you have now figured out why the “cool on” light on your Honeywell thermostat is flashing! If this light has been flashing for more than five minutes, you now know what it means and how to fix it. Getting it up and running again in no time will save you money!


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