Honeywell Thermostat Blinking Cool On? | Check These Troubleshooting Tips

Honeywell Thermostat Flashing “Cool On” Troubleshooting Guide

Are you experiencing the Honeywell thermostat cool on blinking problem? If so, you’re not alone. This is a common air conditioning issue. While this problem can be a hassle to deal with, there are a few troubleshooting tips that can solve the issue right away.



If you’re dealing with the Honeywell thermostat cool on flashing, keep reading to learn some troubleshooting steps.

What does it mean?

When your thermostat display says “Cool On,” this is an operation mode that’s controlled by your thermostat. When you see this cooling message, it essentially means your AC unit is working to pump cool air into your home. However, if you notice your Honeywell thermostat blinking cool on for long periods of time and you don’t feel any cool air, there could be an issue on your hands.



On some occasions, this “Cool On” message may flash for only a short time. If it stops flashing after 5 minutes and the cool air is restored, you have nothing to worry about. This feature is actually a safety measure that’s built into the unit. It’s intended to give your compressor about 5 minutes to fire up the system components. You may also see this message if your AC unit loses power.

Troubleshooting Steps

If the 5 minutes passes up and you’re not feeling any cool air from your vents, you may need to troubleshoot the problem.

You can always call an HVAC technician to handle everything for you, but we recommend trying the following troubleshooting steps first:

Crank thermostat down to the lowest temperature

The first step is to determine if your system is cooling at all and if it can control it. To check this, turn down your thermostat to its coldest setting. After setting it to the minimum temp, double-check the mode is set to ‘Cool.’ Also, make sure the fan setting is set to ‘Auto.’ Once you’ve made the adjustments, wait at least an hour until you feel cool air from your vents. If there’s no improvement, proceed to the other troubleshooting steps.

Check the mode on your thermostat

On some occasions, a Honeywell thermostat can be in the wrong setting. For instance, if there was a recent power outage, this can cause your thermostat to switch to the ‘Setup’ mode. This can lead to the dreadful Honeywell cool on flashing problem.



If you notice the system is in the ‘Setup’ mode, make the necessary change. You should also look at the time on your thermostat. If it’s wrong or not set at all, make sure to set the correct time. By ensuring your system has the proper settings, the problem can disappear in a matter of minutes.

Change the batteries if needed

Obviously, your thermostat needs healthy batteries to operate effectively. If the batteries are dying, your thermostat could be blinking the “Cool On” message. When your thermostat doesn’t have enough power, it won’t be able to start the cooling or heating process.

To properly check your batteries, look for the “Battery Low Indicator” message on the thermostat display. Once you see this message, you usually have two months of power left on the device.

Make sure your AC unit has power

Once you’ve gone through the previous troubleshooting steps, it’s time to make sure everything has power. After checking the batteries in your thermostat, head over to your indoor and outdoor unit to ensure they’re powered up. It’s also a good idea to check connections, sockets, and power supplies. Make sure everything is hooked up properly and receiving power.



It’s also important to listen for any unusual sounds. This could indicate a system problem. Another tip is to check the circuit breaker. You can switch the power on and off, which might help. Checking for a blown fuse is another approach you can take.

Check air filter

A dirty or clogged air filter can result in a number of system issues. Furthermore, they can also drive up energy bills and decrease the longevity of your AC unit. As a general rule of thumb, change your air filter every three months. However, you may need to change it more often if you have pets or allergies.

Examine AC coils

Dirty air conditioning coils can also lead to a Honeywell thermostat blinking cool on. Just like your air filters, dirty coils can have a huge impact on your cooling comfort. But since coils are checked far less often than filters, this could be the source of the problem. Over time, your coils can easily attract tons of dirt, which restricts airflow. This can cause many problems in the entire system. That said, it’s smart to inspect these coils and clean them if they appear dirty. You should also clean off any dirt or debris on the fins in your system.

Reset the thermostat

When all else has failed, try resetting your thermostat. Just like all machines and devices out there, sometimes a simple reset can do the trick. However, since resetting your thermostat wipes away all settings and programming, make sure you take that into account. To remember your desired settings, some homeowners write them down before the resetting process.



If you’re still having no luck, call an HVAC professional. They have tons of experience with these system issues, and they can possibly fix the problem within minutes.