Honeywell Thermostat Blinking "Cool On"? (Here's Why!)

Honeywell thermostats are among the best on the market because of their user-friendly display and reliability. The display is one of the highlights of Honeywell thermostats because useful information is readily available and it’s easy to use. So, what does it mean when your Honeywell thermostat is blinking “Cool On”?

The “Cool On” message will appear on your Honeywell thermostat if the batteries are dying or there is faulty wiring. Your Honeywell thermostat can also display “Cool On” if your AC needs to give your compressor a 5 minute cooldown time to protect it. A bad blower motor or dirty air filter can also cause a blinking “Cool On” to appear on your Honeywell thermostat.

Luckily, each of these problems has a quick solution ranging from waiting 5 minutes to replacing your AC filter. There is nothing to worry about if your Honeywell thermostat reads “Cool On”. Follow along as we explore what you can do if your Honeywell thermostat is flashing “Cool On”.

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A blinking “Cool On” message can appear due to dying batteries, a power surge, or a power outage. Thermostat batteries last for an average of 10 months, so it is easy to tell when dead batteries are the culprit. Sometimes, a Honeywell thermostat can bounce back after a power outage without requiring a reset.

Power surges and power outages can disrupt your HVAC system unless you reset it in most cases. Your Honeywell thermostat may flash “Cool On” even when it’s brand new if it wasn’t installed properly. Luckily, the solutions for each of these problems are largely the same.

Every air conditioner has an air filter, and it can accumulate dirt and debris at different rates. However, an AC filter can gunk up quickly during periods of heavy use during the winter or summer. Dirty and clogged air filters can cause your Honeywell thermostat to display a “Cool On” message.

A dirty AC filter can cause several problems, such as thermostat malfunctions, high electricity bills, and frozen evaporator coils. An unexplainable “Cool On” message from your Honeywell thermostat can often indicate it’s time to replace the filter and prevent expensive bills and even mold or mildew.

HVAC professionals recommend that you replace your AC filter once per month or two months so that your system works properly. Otherwise, a dirty AC filter can cause your Honeywell thermostat to malfunction, read “Cool On” when it shouldn’t, or temporarily stop working.

You can also clean your AC filter with a mixture of equal parts water and white vinegar to fix your HVAC system and Honeywell thermostat.

You can spend as little as $10 to replace an AC filter yourself, or at least $40 to hire a professional. Replacing your own AC filter is easy and only takes a moment so it is worth saving the money.

Faulty wiring can make a Honeywell thermostat malfunction and even read “Cool On”. Problems with wiring can occur even after installation if something gets knocked loose. However, wiring problems are most common for homeowners that wire their own thermostats and AC units.

That is why it is best for HVAC professionals to wire a thermostat to your AC, but DIY installations don’t always go wrong. Wiring problems can be dangerous, but they can also cause your thermostat to enter a “Cool On” or delay period without explanation. If your air filter is fine and you didn’t have a recent power outage or surge, the “Cool On” message could be due to faulty wiring.

Your AC blower is responsible for the airflow in your home, and it can negatively impact your HVAC system if it goes bad. The most common problem with AC blowers is that the motor goes bad. An AC blower motor lasts for an average of 12 years, but it can go bad before then.

Your Honeywell thermostat will likely malfunction if there is a problem with the blower motor. That is because your thermostat tries to turn the blowers on with no success. A blinking or static “Cool On” message can appear if your Honeywell thermostat unsuccessfully tries to turn on the blowers.

Related Questions

Why is the auxiliary pump of my thermostat coming on while displaying cool?

It can be quite confusing to have your home blowing hot when you set the temperature to low. There are a few possible reasons your auxiliary heat is coming on during the AC mode. But the issue is most likely with your wiring. The aux heat wire might be wired with the heat pump, thereby confusing the heaters, and making them come on in cool mode.A quick check on the terminal wiring is the right step forward. If the two are both on a terminal, move the aux wire to another terminal. Make sure the aux heat wire is in the W1 terminal, and the other is on W2.

Do I need to reset my thermostat settings if there is a power outage?

The Honeywell thermostat is designed with permanent memory storage, which helps store its program, schedule, and customizations. Every user setup is also stored. Therefore, there is no need for a reset after a power outage. When power gets restored, your thermostat will automatically pick up where it left off.

The most common problem is that your compressor needs 5 minutes to cool down if your Honeywell thermostat is blinking “Cool On”. Otherwise, you may need to clean or replace your AC filter if it is clogged with debris. Simply reset your circuit breaker if your Honeywell thermostat says “Cool On” but won’t work after a power outage.

Inspect the wiring from your thermostat to your AC if no other solution works. Hire an HVAC professional if you have a problem with your blower fan motor and need to replace it.