Honeywell thermostat cool on blinking

Honeywell thermostat is a popular choice among thermostat users. But you might have seen that your Honeywell thermostat cool on blinking started, but the blinking does not turn off.

If this is the case, you have come to the correct place because our troubleshooting guide will focus on this matter today. There can be many issues associated with this like the thermostat says cool on but no air, the thermostat is blinking, and many more.

Do not worry, as we will focus on every problem related to your Honeywell thermostat blinking cool-on and a guide to solving this problem in no time.

What is meant by “Cool On”?

Before we go and troubleshoot the cool on blinking issue, let us get a quick idea about what is Cool on.

One of the operation modes controlled by your thermostat is the Cool On indication. It merely notifies you that it has begun working on your HVAC system, and your home’s air conditioning has been turned on.

You shouldn’t be too concerned if the Cool On indicator blinks for just a few seconds. It’s a safety feature of the system. It keeps your compressor from being harmed by allowing it to cycle its components for around 5 minutes. It can also happen if there is a power outage.

Troubleshooting: Honeywell thermostat cool on blinking

Honeywell thermostat cool on blinking

So, when your Honeywell thermostat is in the blinking stage, it shows Cool-On for more than 5 minutes – But there is a feeling that the surrounding area is not cooling down, there is no cool air coming through the system either; you might need to fix the problem.

Down below, we will divide the troubleshooting procedures into six quick steps.

Keep the thermostat to the lowest setting

Keep the thermostat to the lowest setting

The first step is to determine whether or not the thermostat can adjust the temperature. It will be the indicator of whether your Honeywell thermostat needs fixing or not.


  • Please set it to the lowest temperature possible.
  • Make sure it’s in the cool mode.
  • Make sure the fan is set to ‘Auto’ as well.
  • Wait at least an hour after making the modifications to experience cold air coming from your vents.
  • Allow it to sit for some time to observe if anything happens or the temperature changes.

Check whether the thermostat is in setup mode or clock set

Check whether the thermostat is in setup mode or clock set

The mode of your Honeywell thermostat can get changed due to a power cut. You will see that it is flashing cool on after a power outage, and the thermostat will go in “Setup mode.”

The “cool on” light may blink at you repeatedly due to this. This issue should be resolved once you’ve reset your thermostat. If your thermostat’s time is off or not set, double-check it.

This might be a reason why your Honeywell thermostat isn’t operating properly. Go through your settings and make any necessary adjustments.

Check the batteries

Honeywell thermostat cool on blinking-Check the batteries

The thermostat will not be able to start cooling or heating if the batteries are insufficiently charged.

If this is the case, you must replace the thermostat batteries. If you do not change these batteries, then the thermostat won’t heat or cool your home.

Because thermostat batteries last on average for ten months, it’s easy to spot when they’re dead. It’s time to change the batteries if they’re weak. Check whether the “battery low” indicator is blinking on display. Replace the battery within two months of receiving the notification.

However, if your thermostat runs on 24VAC and your thermostat can’t change temperature properly or doesn’t operate properly, you should check the wirings. You will need to turn the power off and remove your thermostat from the wall.

To ensure that everything is in working condition, check the thermostat for the C-wire.

Dusty Air Filter

Dusty Air Filter

A blocked or filthy air filter can cause a variety of system problems; Your thermostat, equipment, and electricity bill will all be affected, including air quality. An AC filter can quickly get clogged during high-use seasons, such as winter or summer.

Hence, a Honeywell thermostat can show a cool message due to a dirty and blocked air filter. As a result, this is a filter message that you should change your AC Filter every three months to ensure that your system functions correctly.

Are your AC coils dirty?

You might think about the relation between a dirty ac coil and your Honeywell thermostat being in the blinking stage. But, to your surprise, dirty AC coils do affect the performance of a thermostat.

Your coil will gather dirt over months or years of operation, preventing optimal airflow. It won’t be as effective at absorbing heat and cooling the air as it once was.

Do not be concerned, as cleaning AC coils is a simple task. If there is build-up on the fins of your AC unit’s coils, it has to be cleaned.

Before cleaning the coil, make sure the device is turned off; clean the space surrounding it as well so that the coils do not become clogged again.

Check whether or not the HVAC system has enough power

Check whether or not the HVAC system has enough power.

Even after following all the steps above, your thermostat is still not cooling down or heating up the room. You need to check the HVAC system. Check for power in components such as the fans or air handler, furnace, and air conditioner.

Make a note of any weird humming or clicking noises when examining your Honeywell thermostat. This might be a sign that something else isn’t right.

Ensure to check your thermostat equipment thoroughly. Examine the power supply, connections, and sockets, among other things. Check to see that they’re correctly plugged in, the switches are switched on, and everything receives the necessary amount of power.

Make sure there are no errors with the circuit breakers as well. To check additional technical parameters, try shutting off the circuit breaker and turning off the unit. Also, see whether anything obstructs or prevents the device from operating correctly. Using a voltmeter to check the blow fuses is also a good idea.

Frequently Asked Questions

So, far we have discussed troubleshooting tips for thermostat cool on blinking issue. But you still might have some questions wobbling around your head, and in this section, we will try to answer that.

How to reset a Honeywell thermostat?

Answer: The process for resetting your Honeywell thermostat varies depending on the model. If the C-wire powers your thermostat, turn it off first; if your model includes a Menu button, press or hold the button for a few seconds to access Reset, Factory, or Factory Reset options. It may be found under the Preferences menu on some models.

But keep in mind as a factory reset will erase all stored data and setting on your thermostat. So, make sure to create a note of any setting you want to restore.

How to set Honeywell thermostat to cool

Answer: If you wish to make your house cooler, you must manually adjust the Honeywell thermostat’s temperature. To turn the fan on or off, press the “Fan” button. Then, to place the thermostat in Heat, Cool, or Off mode, hit the “System” button. Push the button one more to alter the setting.

The temperature settings are controlled via the up and down arrow buttons on the right side of the display. To set the thermostat to a higher or lower temperature, push the up or down buttons.

Should I reset the Honeywell thermostat settings after a power outage?

Answer: No, there is no need for that as permanent memory storage is included in the Honeywell thermostat, allowing it to save its program, schedule, and adjustments. Every user’s configuration is also saved. Your thermostat will resume from the old stored settings when the electricity comes back.

Short Tips

Honeywell thermostat cool on blinking-Short Tips
  • Checking user manual: Before troubleshooting any issues, the first and foremost work is to check the instruction manual for your specific thermostat model. The cryptic messages on your thermostat’s display aren’t always useful. Hence, for answers to frequent difficulties, consult your manual.
  • Professional help: Sometimes, it becomes impossible to solve thermostat problems at home by yourself, and that is when it’s time to call a professional technician.

Damaged wiring, a defective capacitor, a blocked sensor, or a blown fuse are common problems that a professional technician can fix. The compressor, condenser, or fan motor in your system may also need to be checked.

If this is a brand-new installation, the wirework should be double-checked for proper matching. In addition, your thermostat must be properly adjusted for your system. That is something that your professionals can assist you with


Honeywell thermostat cool on blinking is a very common issue for Honeywell users. If you do not know the proper troubleshooting methods, you can get tensed over something very normal, and you might even want to go for a Honeywell replacement. But there is no need for that as we wrote this troubleshooting guide hoping that it will help you solve the Honeywell thermostat problem within no time and without any additional cost.

More thermostat articles from Protroubleshooting,

Abdulla Zatar
About Abdulla Zatar

Hi, I’m Abdulla! Your go-to tech troubleshooter! Sharing my knowledge so that you can fix your tech issues with ease. Let’s make fixing things easy and fun!

Leave a Comment