Honeywell Thermostat Troubleshooting Guide

Honeywell is one of the most relied upon names in HVAC thermostats in the United States. Since their start in 1906, they have provided quality thermostats for homes and commercial purposes nationwide!

This can be considered one of the essential parts of your heating and cooling as it relays the need for service in your house. How can you troubleshoot it if there is a problem?

After installation, it is vital that you keep the manual. Should any issues arise in your thermostat, Honeywell’s thermostat manual can relay all troubleshooting methods for your particular system. Each system has its own steps for resetting and codes that may be attributed to specific errors.

Sometimes, however, you need fast quick answers as to what to do to get your thermostat and system back online. Reading through a manual can take time.

Compiled here are the top troubleshooting questions about Honeywell thermostats, their solutions, and the reasons that these may happen to your system. 

How to Reset Honeywell Thermostat

Our first instinct with a device is to reset it if we believe it to be malfunctioning.

Whether it is due to poor air circulation or a sudden jump in your electric bill, a reset can be a great first step to seeing if you can rectify the problem.

Honeywell thermostats have easy steps that you can follow to reset your thermostat quickly.

The thermostats come with several different resetting options depending on your needs, including Factory Reset, Schedule Reset, WiFi Reset, and HomeKit Reset.

While handy, WiFi Reset and HomeKit Reset are used to reset the connection between your system and the WiFi and your Apple account, respectively, and not used frequently.

To fix issues, you will have to focus on a Factory Reset or possibly a Schedule Reset. Different thermostats have different steps to accomplish this, as detailed below.

Keep in mind, if you are unclear on how to set your system back up after your complete the reset, it would be a good idea to have an HVAC professional on hand.

If you have a smart thermostat, it may be a good idea to ensure you have the proper application downloaded ahead of time to complete the reset process via smartphone.

Keeping your app up to date can ensure that the reset and reconfiguring go smoothly and may even retain some of your previous data to reduce the setup time.

Honeywell Thermostats T5+/T5/T6 

Model NumbersHow to Reset
RCHT8610WF
RCHT8612WF
TH6320WF2
TH6220WF2
Find the Menu Button on your system. Press and Hold it. Next, search your options by pressing the [Symbol] button and find Reset. Reset your system. Reconfigure with the Honeywell Home Mobile app or via the thermostat’s screen.

Honeywell Thermostat Lyric Round/Smart

Model NumbersHow to Reset
TH8732WFHFind the Cloud Icon. Press and hold it. Scroll using the Down Arrow until you see “Reset.” Select Reset. Reconfigure using the Honeywell Home Mobile app or using the plus icon on the device. 

Honeywell Thermostat Is Not Cooling

When you turn on your AC, you expect to hear the whir of your system as it begins blowing cool air almost immediately. What if you set the thermostat and there is no cool air?

First, assess whether you have external factors, such as peak hour downtimes from your electric company. They may have set limitations on power usage if you are on a saving program.

Next, check your thermostat. As you do so, ask yourself the following questions:

  • Is it set to cool?
  • Is the set temperature higher or lower than the current room temperature?
  • Are there any flashing indicators?
Thermostat showing temperature on display

If your system is set to cool, the ambient temperature is higher than your desired temperature, and there are no flashing signs, the problem may lie with your HVAC system or the thermostat’s installation.

To check your HVAC system, first ensure that the circuit breaker was not tripped, causing a lack of power. This is a simple fix and could save you a lot of time if it is the case. 

Next, take a look at your system and see if there is anything awry. This could be a furnace door being open or a debris blockage that is easy to remove. 

Finally, consider your thermostat’s installation. If this is a new thermostat, there may have been a fault in its initial setup, such as not connecting all the proper wires to it or not being compatible. 

At this point, contacting an HVAC professional can ensure the Honeywell thermostat is installed correctly and that your HVAC system is in good condition. 

Honeywell Thermostat Error Codes

Error codes are a fantastic way for your thermostat to communicate issues with the user or technician in shorthand. When first seeing an error code, the initial reaction is to panic, especially with a system as important as your Honeywell thermostat. 

After all, these codes are a string of numbers and sometimes letters that appear to be in a strange computer language. 

Conveniently, the company provides you with a way to translate the codes to understand the problem. At initial installation, make sure you hold on to your manual.

In the back, there usually is a tabled list of every error code your system will provide as well as the issue and the solution for your convenience. They also offer a frequently asked question section to help you.

If you accidentally misplaced your manual, no worries! Many of the manuals can be found online in PDF format.

Thermostat manual paper

To find these, you may want to visit the Honeywell Home Resideo website. Alternatively, your smart device’s app can provide fast troubleshooting solutions to help you get your system back to its best in no time. 

What if you cannot seem to find the manual for your model? The best course of action at that time is to contact your HVAC technician. They can determine the meaning of the code and repair the problem. 

They can also indicate if it is time for a newer model for your home. If you have a T5 or T6 Honeywell Thermostat, there are some standard codes you may see.

Honeywell T5 Series Error Codes

CodeIssueSolution
164The heat pump requires serviceContact HVAC professional
168WiFi radio errorContact HVAC professional
171Set date and timeAdjust these settings for your system scheduling 
173Thermostat temperature sensor errorContact HVAC professional
175AC power resumedNothing to be done
181/182Replace air filterAdd a new filter and then dismiss the code
184Get a new humidifier padAdd a new pad filter and then dismiss the code
185Replace dehumidifier filterReplace the filter and then dismiss code
187Rinse or replace ventilator filterInstall a new filter and the clear the code form your system
188/189Replace UV bulbContact HVAC professional
210Register online for outdoor temperatureUsing the Lyric app, finalize this setup and then check to make sure everything is running smoothly
388Register online for remote access and exterior temperatureUsing the Lyric app, finalize this setup and then check to make sure everything is running smoothly
399No InternetCheck your Internet settings. Assess that your internet is running correctly
400No WiFi signalGive your system time to reconnect and make sure WiFi is running correctly
508WiFi not connectedUse the Lyric app to set up and ensure connection between your router signal and device

Courtesy of Resideo, a Honeywell Trusted Partner

Honeywell T6 Series Error Codes

CodeIssueSolution
164The heat pump requires serviceContact HVAC professional
168WiFi radio errorContact HVAC professional
170Internal memory errorContact HVAC professional
171Set date and timeAdjust these settings for your system scheduling 
173Thermostat temperature sensor errorContact HVAC professional
175AC power resumedNothing to be done
177Indoor temperature sensor errorContact HVAC professional
178Outdoor temperature sensor errorContact HVAC professional
181/182Replace air filterAdd a new filter and then dismiss the code
183Clean humidifier tank and install a new water filterReview and handle tasks requested by the system and then dismiss the code
184Get a new humidifier padAdd a new pad filter and then dismiss the code
185Replace dehumidifier filterReplace the filter and then dismiss code
186Rinse ventilator coreReview and handle tasks requested by the system and then dismiss the code
187Rinse or replace ventilator filterInstall a new filter and the clear the code form your system
188/189Replace UV bulbContact HVAC professional
210Register online for outdoor temperatureUsing the Lyric app, finalize this setup and then check to make sure everything is running smoothly
388Register online for remote access and exterior temperatureUsing the Lyric app, finalize this setup and then check to make sure everything is running smoothly
399No InternetCheck your Internet settings. Assess that your internet is running correctly
400No WiFi signalGive your system time to reconnect and make sure WiFi is running correctly
508WiFi not connectedUse the Lyric app to set up and ensure connection between your router signal and device

Courtesy of Resideo, a Honeywell Trusted Partner

Honeywell Thermostat Display Not Working

A Honeywell thermostat is your intermediary, providing a messaging method from your directly to your HVAC system

From here, you can ask it to heat and cool your home as necessary and even get information about your HVAC system’s wellbeing. So what if your thermostat stops relaying the information?

Two of the most common concerns regarding thermostats is when the display is either blank or dimmed to the point where discerning information feels impossible. 

These issues can set you at odds with your system as you can no longer dictate whether you need the HVAC unit to run or not. It is not unheard of that a display stops working, so do not panic. 

There are simple troubleshooting solutions that you can take before you have to contact a professional. 

By diagnosing the problem and doing a few simple tasks, you may even be able to forgo the need for a service appointment if the issue resolves!

Below are ways to assess and possibly solve these two most common issues. 

Display is Blank

You go to adjust the temperature and realize your thermostat is blank. No matter how you tap on it or press available buttons, it just does not light up. 

This can be stressful since your Honeywell thermostat is your primary interface to communicate with your AC. However, there may be a simple solution to this issue.

  1. Check the batteries: Many systems use batteries either as a backup or to power the main display. When your thermostat is blank, go ahead and swap the old batteries out for a new set. If this is the problem, your system will light back up!
  2. Check the breaker: A power surge can trip the circuit your Honeywell thermostat is on, leading to a shutdown. This may also affect other portions of your home and even the HVAC system. Check the box and see if the switch is flipped. If so, turn it back on, and you should be good to go!

These are the easy first-line actions you can take to get your system back online. However, if you try these and your thermostat is still not back online, it is time to consider more significant issues. 

Man handling thermostat

Your HVAC system may have a safety switch trip, which has lead to a short. At this point, getting an inspection can tell you if your HVAC system is the culprit and has a problem.

The worst-case scenario is that your thermostat is just broken. As a piece of machinery and a frequently used item, they can wear over time and require replacement. 

You can expect a thermostat to last about ten years before replacement may be necessary. If this is the case, speak with your HVAC professional about what Honeywell thermostat may be right for your home. 

Display is Dim

To adjust your temperature, you have to see what you are doing. If your thermostat is dim, it can make it challenging to get your system running the way you want. 

While this may have been a sign of a fault within the system in the past, this is, in fact, a built-in feature for many of the modern Honeywell Thermostat systems.

As the thermostat idles, its brightness will be lowered until you need to interact with it.

As it is a built-in feature, you can adjust the brightness of your Honeywell Thermostat while idling to your liking. Simply navigate the menu to brightness and change until you are happy. 

The settings range from zero to five, with five being the brightest setting available. This is just one of the many ways the Honeywell Thermostats are designed to fit your needs.

What if the brightness adjustment does not take? If the adjustment does not work, consider replacing the batteries as low visibility may be a sign of power loss.

Check the manual for what type of battery your system takes and then follow instructions for replacement. Your system should be back to its best after you replace them and allow you to adjust again as necessary. 

The last step to take if the problem appears unsolvable through conventional means is to contact an HVAC professional.

The problem may lie further within the thermostat mechanisms, such as a bulb or a wire that does not make a proper connection, causing a dimming effect. 

Honeywell Thermostat Won’t Turn off AC

A continuously running AC can freeze your home and eat up a lot of electricity. While most of the time, it will be an issue with the HVAC system itself, there are instances where the problem may lie with your thermostat.

In these cases, it will more than likely be a damaged wiring issue or a defect in the thermostat itself.

Whether a new installation or old, damaged wiring can occur in your system due to factors like rodents, poor insulation, accidental nails, and even weed whacking around your home!

Ceiling HVAC AC

The best way to check for damaged wiring is by taking a look at the leads to your compressor or by checking in the walls of your home if possible.

A defective thermostat may tell your system to run continuously as if the air has not cooled in the home.

The best way to determine this is to gently and carefully remove the wire from the Y panel in your Honeywell thermostat. If you remove this and your system kicks off, the problem lies with your thermostat.

Immediate action to stop the continuous running is to switch your HVAC system off at the breaker. This is a temporary measure to keep your home from expending more energy until you can get an HVAC professional out to inspect or repair the thermostat.

After that, a simple switch back on will power your system once more. 

Honeywell Thermostat Cool ON Is Flashing

Flashing lights on a thermostat can be extremely unsettling, especially if you are unsure what they mean.

One of the most common instances of this is when you need cool air sent to your home, but you see the thermostat’s “Cool ON” or a little snowflake flashing in the corner. What could this mean?

These indicators are your system’s way of typically signaling that it is sending a request to your HVAC system to send some cool air. However, when it is flashing, it is saying that the system is in delay mode. 

This is a protection feature installed for your compressor and can last up to five minutes. The best course of action is to wait patiently to give your compressor time to prevent short cycling

What is short cycling? This is a term used to describe when your system turns on for a short period of time, turns off, and then turns on again a few minutes later.

This can cause a problem as the more often it works like this, the harder your HVAC system needs to work. The delay simply gives your system time to cool off and relax. 

If the flashing indicators is a frequent and persistent issue, it is time to call a technician.

There may be wear and tear or a fault that is causing your HVAC system to work infrequently. Such instances make it, so your home does not get the cool air it needs as regularly while more and more electricity is consumed for little results. 

Keeping Your Honeywell Thermostat At Its Best

When you choose a Honeywell thermostat for your home, you choose reliability and convenience.

These thermostats are designed to help you quickly get the HVAC service you need in the house and keep you and your loved ones as comfortable as possible.

You get the ease of use in the palm of your hand and peace of mind that no matter the weather, your home will be just right for you.

The manual that comes with your thermostat can save you a lot of time and heartbreak when determining what is causing a problem.

Honeywell puts possible error codes, frequently asked questions, and even the solutions to the most common issues in the guide. Once your system is installed, hold on to the manual or download a PDF version off of the internet in case of an emergency. 

While troubleshooting some problems may be easy, keep in mind that all HVAC systems require service from a professional from time to time. Contacting an HVAC technician for installation and error codes that you cannot handle on your own can not only get your system running smoothly but can keep you in your warranty’s good graces. 

When replacing your old thermostat, there is no better option than a new Honeywell thermostat model. Get connectivity throughout your home and the ability to control comfort from your smartphone with smart thermostats. 

Whether you want the smart home experience or a model that is simple to interact with, Honeywell has a thermostat that will be perfect for you.