How to change batteries in Honeywell t6 pro thermostat? (QUICKEST way!)

Unlike other thermostat manufacturers like the Google Nest and Amazon thermostat, Honeywell has been around for a very long time! 

Starting from Furnace regulators to thermostats and now smart thermostats, Honeywell has maintained its impact in the market. According to my personal observation, Honeywell users report lesser issues as compared to other Smart thermostats.  Moreover, Honeywell thermostats are highly compatible even with uncommon HVAC systems like the Geothermal system

Most Smart thermostats, including the Honeywell T6 pro thermostat use batteries as a backup power supply. These batteries, although not used primarily for power, can run out and need to be replaced. How to change batteries in Honeywell T6 pro thermostat? In this article, I will provide you with a step-by-step guide on how to do it.   


How to change batteries in Honeywell T6 pro Thermostat? (Step-by Step)  

A lot of Honeywell errors are caused by low batteries. Hence, regularly changing your thermostat batteries is vital for overall functionality of the thermostat and your HVAC. You can change your Honeywell T6 thermostat’s battery in this way: 


Step 1: Take off the thermostat face plate

Remove face plate
Image by Todd’s Garage


First, we need to open Honeywell thermostat to change batteries. Hold the Honeywell thermostat’s front plate, and gently pull it away from the wall (towards yourself). 

Make sure that your hand makes a 90 degree angle with the wall while pulling the face plate. This will ensure that you do not damage any connecting pins on the back side of the face plate.  


Step 2: Locate old batteries at the back side of the face plate 

Locate old batteries
Image by Todd’s Garage


Now that you have removed the face plate, flip it to see the batteries at the back side. 

There are two AA (Double A) batteries which need to be replaced.   


Step 3: Remove the old batteries and replace with new ones 


Remove old batteries
Image by Todd’s Garage


Simply remove the old batteries. Grab two new AA batteries and plug them into the place of old batteries.  

Make sure that the Plus sign on the battery matches the plus sign on the Honeywell thermostat. Do the same for minus signs. 


Step 4: Reattach the face plate to the base plate 

Reattach face plate
Image by Todd’s Garage


Now that new batteries are installed, all we need to do is reattach the face plate to the base plate of the Honeywell T6 thermostat. 

 Once again, make sure that you hold the face plate against the base plate at a 90-degree angle. Align all the connecting pins to their subsequent holes (in the base plate).  

Now, gently push the face plate to fix the thermostat back to its original position. You will hear a “click” sound, ensuring that you have successfully reattached the Honeywell T6 thermostat. 


Frequently Asked Questions regarding Honeywell Thermostat’s battery


How do I know if my Honeywell thermostat battery is low? 

 To signify that your Honeywell thermostat’s battery is low, a low battery indicator will appear on it.  

Alternatively, “BATT” will be seen on the middle of the Honeywell Thermostat’s screen. This is an indicator that your Honeywell thermostat needs a battery replacement. 


How long do the Honeywell thermostat’s batteries last?  

The Honeywell thermostat’s batteries should last for at least 8 months. However, usually the batteries last for around a year.  


How does the Honeywell thermostat get power? 

 The Honeywell thermostat operates at 20-30 VAC, which is supplied to the R/RC terminals and returns through the C terminal.  

A C wire is therefore necessary for the Honeywell thermostat to power itself. However, there are backup batteries present in the thermostat which can power it for a while the C wire is not supplying power. 


What happens when Honeywell thermostat battery dies? 

When your Honeywell thermostat’s battery is dead, it will not function properly. You won’t be able to program it, and the thermostat won’t be able to control your HVAC system.  

Not only that, but any pre-programmed settings of your Honeywell thermostat will be lost if the battery dies out. In this case, it is absolutely necessary that you replace the batteries with new ones.  



Now that you know how to change batteries in Honeywell T6 pro thermostat, you can change them yourself! Backup batteries are extremely important for the correct functionality of a thermostat. Therefore, I would advise you to keep changing them periodically (after every 8-12 months). I hope this article was useful for you. 

Happy Smart Homing!   

Stefen Turner

Hey! My name is Stefen and I am the founder of Smart Home Hunt. Prior to starting this blog, I used to work as a Full-Stack Web Developer in the field of Internet of Things (IoT).

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