SOLVED: New Honeywell Thermostat Blowing Hot Air on Cool

Are you experiencing the frustrating issue of your new honeywell thermostat blowing hot air on cool mode? You’re not alone. 

It’s a common problem that can leave you feeling uncomfortable, especially during hot summer days. But don’t worry; we’re here to help.

In this guide, we will provide you with expert tips and solutions to resolve the hot air issue with your new Honeywell thermostat. 

Let’s get started with the first step in resolving this issue: understanding why it occurs.

Why is your Honeywell thermostat set to cool but heating?

Before we dive into the expert tips for resolving Honeywell thermostat cool on but not working issue, it’s crucial to understand why this problem occurs. 

Several factors can contribute to your new honeywell thermostat blowing hot air on cool. Let’s explore some of the common reasons:

Incorrect Thermostat Settings

Sometimes, the thermostat settings may have been accidentally adjusted to heating mode instead of cooling. 

This simple oversight can result in your thermostat delivering warm air.

Temperature Sensor Issues

Your thermostat relies on temperature sensors to gauge the ambient temperature. 

If these sensors are dirty, malfunctioning, or incorrectly placed, they can lead to inaccurate readings and hot air output.

Installation Errors

Improper installation of your Honeywell thermostat can disrupt its functionality. 

Incorrect wiring or loose connections can cause the system to misbehave, including blowing hot air when it should be cooling.

Software or Firmware Problems

Just like any other electronic device, thermostats receive updates to improve performance and address issues. 

Outdated or buggy software can affect your thermostat’s ability to maintain the desired temperature.

Compatibility Issues

If your thermostat is not compatible with your HVAC system or other components, it can result in unexpected heating instead of cooling.

Mechanical Problems

In some cases, there may be mechanical issues within the thermostat itself, such as a malfunctioning valve or relay.

New Honeywell Thermostat Blowing Hot Air on Cool Fixing Guide

One of the most common reasons for your new honeywell thermostat cool on but not working is incorrect thermostat settings. 

To resolve this issue, follow these expert tips to ensure your thermostat settings are configured correctly:

Mode Selection

   – Locate the mode selection switch or button on your thermostat.

   – Ensure it is set to “Cool” or “Cooling” mode. This tells your thermostat to activate the air conditioning system for cooling.

Temperature Settings

   – Check the temperature setting on your thermostat. It should be set to a temperature lower than the current room temperature.

   – If it’s set too high, the thermostat may think your room is already at the desired temperature and won’t activate the cooling system.

Fan Setting

   – Verify the fan setting. It should be set to “Auto” rather than “On.” In “Auto” mode, the fan runs only when the cooling system is actively cooling the air.

   – “On” mode keeps the fan running continuously, which can circulate already cooled air, but it won’t initiate cooling if the thermostat is set incorrectly.

Check for Hold or Override

   – Ensure there are no temporary holds or overrides on the thermostat settings. These temporary adjustments can disrupt your cooling schedule.

   – Reset the thermostat to its programmed schedule or the desired temperature.

Battery Check (If Applicable)

   – If your thermostat uses batteries, check if they need replacement. Low or dead batteries can lead to improper functioning.

   – Replace the batteries with fresh ones and reset your thermostat.

Troubleshooting Installation for New Honeywell Thermostat Blowing Hot Air on Cool

Incorrect installation of your Honeywell thermostat can be a significant factor in the hot air issue. 

To troubleshoot installation errors and ensure your thermostat is properly set up, follow these expert tips:

Power Off

Before checking the installation, turn off the power to your thermostat and HVAC system. This ensures your safety during the inspection.

Examine Wiring

   – Carefully remove the thermostat cover to access the wiring.

   – Ensure that the wires are correctly connected to their corresponding terminals. Refer to your thermostat’s manual or labeling for guidance.

   – Tighten any loose wire connections and make sure none are exposed or damaged.

Compatibility Check

   – Verify that your Honeywell thermostat is compatible with your HVAC system. Check the user manual or the Honeywell website for compatibility information.

   – If it’s not compatible, you may need to consider a different thermostat or consult a professional for a compatible installation.

Level and Position

   – Check the thermostat’s positioning on the wall. It should be level and securely attached.

   – Ensure there are no obstructions or drafts around the thermostat, as this can affect its temperature readings.

Insulate and Seal

   – Inspect the area around the thermostat’s base. Seal any gaps or holes in the wall where wires pass through to prevent air leaks.

   – Proper insulation and sealing help maintain accurate temperature readings.

Reconnect and Power On

   – After verifying the installation, carefully reattach the thermostat cover.

   – Restore power to your thermostat and HVAC system.

   – Test the thermostat to see if it now operates correctly in cooling mode.

Software and Firmware Updates for New Thermostat

Keeping your Honeywell thermostat’s software and firmware up to date is essential for ensuring optimal performance and resolving hot air issues. 

Here’s how to manage software and firmware updates effectively:

Identify Your Thermostat Model

   – Begin by identifying the exact model of your Honeywell thermostat. You can usually find this information in the user manual or on the thermostat itself.

Check for Updates

   – Visit the official Honeywell website or use the Honeywell mobile app (if available for your thermostat model).

   – Look for a “Software Updates” or “Firmware Updates” section specific to your thermostat model.

   – Follow the provided instructions to check for available updates.

Download and Install Updates

   – If updates are available, download them to your computer or mobile device as instructed.

   – Connect your device to the thermostat or follow the specific installation process for your model.

   – Install the updates onto your thermostat according to the provided guidelines.

Reconfigure Settings

   – After updating the software or firmware, review your thermostat settings to ensure they are still configured as desired.

   – Some updates may reset certain settings, so it’s essential to double-check and make any necessary adjustments.

Monitor Performance

   – After updating, monitor your thermostat’s performance to see if the hot air issue has been resolved.

   – Pay attention to the cooling mode to ensure it operates correctly.

Safety Precautions During Troubleshooting Honeywell thermostat set to cool but heating

When troubleshooting your honeywell thermostat set to cool but heating, it’s essential to prioritize safety. 

Here are some safety precautions to keep in mind:

Power Off

Always turn off the power to your thermostat and HVAC system before attempting any troubleshooting or maintenance. 

This prevents the risk of electrical shock and ensures your safety during inspections.

Shut Off Gas Supply

If your HVAC system is gas-powered, locate the gas supply valve and ensure it is turned off before working on any components. Gas leaks can be hazardous.

Use Proper Tools

If you need to open the thermostat cover or inspect the wiring, use the appropriate tools, such as screwdrivers, to avoid damaging components or injuring yourself.

Read the User Manual

Refer to your thermostat’s user manual for specific safety instructions and guidelines provided by the manufacturer. 

It may contain important information related to your thermostat’s installation and operation.

Avoid Overloading Circuits

Be cautious not to overload circuits or connect too many devices to the same electrical outlet. 

This can lead to electrical issues and potentially create a safety hazard.

Handle Wiring Carefully

If you’re inspecting or adjusting wiring, handle it gently and avoid pulling or tugging excessively. Damaged wires can lead to electrical problems.

Keep Flammable Materials Away

Ensure there are no flammable materials or objects near your thermostat or HVAC system. Keep the area around these devices clear to prevent fire hazards.


When working with your HVAC system or thermostat, ensure that the area is well-ventilated to prevent the buildup of fumes or gases.

Know Your Limits

If you’re uncertain about any aspect of troubleshooting or maintenance, it’s safer to seek professional assistance from an HVAC technician. 

Attempting complex repairs without the necessary expertise can lead to accidents or further damage.

Carbon Monoxide (CO) Detectors

If your HVAC system involves combustion (e.g., gas furnaces), make sure you have working carbon monoxide detectors installed in your home. 

CO leaks can be life-threatening, so having detectors in place is crucial for safety.

New Honeywell Thermostat Caring Tips for Optimal Performance

Regular Cleaning

Dust and debris can accumulate on the thermostat’s display and sensors, affecting its accuracy and responsiveness. 

Use a soft, lint-free cloth to gently wipe the screen and surrounding areas. Avoid using abrasive or chemical cleaners, as they can damage the device.

Check Batteries

If your thermostat uses batteries, it’s essential to check them regularly. Low or dead batteries can lead to thermostat malfunctions. 

Replace the batteries as needed, typically once a year, or as indicated by the low battery warning.


Calibrating your thermostat ensures accurate temperature readings. To do this, use a separate, accurate thermometer to compare the displayed temperature on your thermostat. 

If there’s a significant difference, consult the user manual or contact Honeywell support for calibration instructions.

Keep Vents and Registers Clear

To allow your thermostat to function optimally, ensure that air vents and registers in your home are not obstructed by furniture or other objects. 

Proper airflow helps maintain consistent temperature control.

Firmware Updates

Honeywell may release firmware updates for your thermostat to improve performance and add new features. 

Check for updates periodically and follow the manufacturer’s instructions for installing them.

Seasonal Adjustments

Adjust your thermostat’s settings seasonally to maximize energy efficiency. Lower the temperature in the winter when you’re away and raise it in the summer.

Consider using programmable or smart thermostats for more precise control.

Protect from Extreme Conditions

Extreme heat, cold, or humidity can affect your thermostat’s performance. 

Install your thermostat away from direct sunlight, drafts, or moisture-prone areas. This helps maintain its accuracy and prolong its lifespan.

Professional Maintenance

If you encounter persistent issues or suspect a malfunction, it’s advisable to seek professional help. 

Certified HVAC technicians can diagnose and repair any underlying problems with your thermostat or HVAC system.

How to Contact Honeywell Support?

If you’ve tried the previous expert tips and your Honeywell thermostat is still blowing hot air when it should be cooling, it’s time to consider reaching out to Honeywell’s customer support. 

Here’s how to effectively contact them for professional assistance:

Gather Information

   – Before contacting support, gather essential information about your thermostat, such as the model number, serial number, and any recent changes or issues you’ve noticed.

   – Be prepared to describe the problem in detail, including when it started and any error messages displayed on the thermostat.

Visit the Official Honeywell Website

   – Go to the official Honeywell website ( and navigate to the “Support” or “Contact Us” section.

   – Look for the customer support contact information, which may include phone numbers, email addresses, or live chat options.

Phone Support

   – If a phone number is provided, consider calling Honeywell’s customer support hotline. This is often the quickest way to get assistance.

   – Be patient and explain your issue clearly to the customer support representative. They may guide you through additional troubleshooting steps.

Email Support

   – If you prefer written communication, you can email Honeywell support with your issue and the gathered information.

   – Provide as much detail as possible in your email to help them understand your problem.

Live Chat (if available)

   – Some Honeywell websites offer a live chat option where you can chat with a support agent in real time. This can be a convenient way to get immediate assistance.

Follow Their Guidance

   – Once you’ve made contact, follow the guidance and instructions provided by Honeywell support.

   – They may ask you to perform additional tests or steps to diagnose the problem accurately.

Warranty Information

   – If your thermostat is still under warranty, inquire about warranty coverage and potential solutions.

   – Be prepared to provide proof of purchase if necessary.

Frequently Asked Questions (FAQs)

How often should I update my Honeywell thermostat’s software or firmware?

It’s a good practice to periodically check for updates, especially when you encounter issues. Updates often include bug fixes and improvements. Refer to our expert tip on software and firmware updates for guidance.

What should I do if none of the troubleshooting steps work, and my thermostat still blows hot air?

If you’ve exhausted all troubleshooting options, it’s advisable to contact Honeywell support or a licensed HVAC technician for a thorough diagnosis and resolution of the problem.

Does my thermostat’s warranty cover issues like hot air blowing during cooling mode?

Warranty coverage can vary by model and region. Check your thermostat’s warranty terms and contact Honeywell support to inquire about warranty-related issues.

Are there any DIY fixes for specific Honeywell thermostat models known to have hot air issues?

Some thermostat models may have specific issues addressed by manufacturer-recommended fixes or updates. Check Honeywell’s official resources for model-specific solutions.


Resolving the issue of your new honeywell thermostat blowing hot air on cool is essential to ensure your home remains comfortable, especially during the warmer months. 

If you’ve exhausted all troubleshooting options and the issue persists, don’t hesitate to contact Honeywell support or a licensed HVAC technician for professional assistance. 

Your comfort and safety are our top priorities, and we hope this guide has been instrumental in helping you regain control over your home’s cooling system. Stay cool!

Scott Maupin