Does the following sound familiar? A few weeks ago your Honeywell thermostat gave you the warning message that the batteries’ power was declining. You have bought new batteries and replaced your Honeywell thermostat’s batteries, but now the thermostat doesn’t work. You immediately wonder whether you’ve damaged the thermostat and, if so, what you have to do now. How do you determine what the fault is, and can you repair the fault yourself? 

A Honeywell thermostat not working after a battery replacement could be due to not inserting the correct batteries, inserting them incorrectly, or following the wrong battery replacement procedures.

For many Honeywell thermostats, for instance, resetting is a necessary first step. Thus, by checking a few aspects, you might find the problem easy to rectify. 

In this article, I’ll discuss different aspects you can check and rectify yourself if your Honeywell thermostat is not working after a battery change. Any one or a combination of the aspects could be the reason why your thermostat is suddenly not working with the new batteries.  The aspects I discuss are in no particular order, so you can do your checking in the order that will suit you the best. 

Aspect 1: Did you buy the best batteries available?

Sometimes batteries – even new batteries – are just not strong enough to allow your Honeywell thermostat to work. Some cheap batteries are often not meant to be used in sophisticated environments and devices. They are not strong enough for a device such as your Honeywell thermostat. 

More expensive batteries are usually designed for high-tech devices and have a “guaranteed” power capacity. More expensive batteries will also work longer. Good thermostat batteries can be in service for up to 2 years.  Therefore it is good practice to buy the best batteries available even if they are more expensive. 

So, when your thermostat is not working after you’ve replaced the batteries and you know you haven’t bought the best batteries available, your problem can probably be solved by purchasing and inserting a better set of batteries. 

Aspect 2: Did you buy the correct batteries?

Sometimes batteries can be the same size but are actually different types of batteries. There are many types of batteries, and Honeywell thermostats require a very specific type of battery. Honeywell thermostats usually use alkaline AA or AAA batteries. 

Especially modern smart thermostats don’t work with all types of batteries. Consult your user manual to find out the correct type of battery your thermostat needs.

If you don’t know which batteries will be the best, it is always safe to replace the existing batteries with exactly the same brand and type that originally came with your Honeywell thermostat.

Aspect 3: Test whether the batteries have any power

Generally speaking, Honeywell thermostats use AA or AAA batteries and most households also have other appliances and devices using AA or AAA batteries. Take your new batteries out of the thermostat and put them in one of these other household devices. 

If the device is also not working with the batteries, the batteries most probably have gone bad. Get a set of new batteries and your problem might be solved.

Aspect 4: Check whether you’ve installed the batteries correctly

If you’ve tested the batteries in other household devices and the batteries have worked in every device except the thermostat, you might have installed the batteries incorrectly. Put the batteries back again after you’ve verified the orientation they should be in. The thermostat’s battery housing should indicate the battery orientation.   

It is important to take note that in most programmable Honeywell thermostats the batteries are aligned in the same direction. They normally have to face up. To make absolutely sure, check the battery holder’s markings. 

If in doubt regarding the batteries’ orientation, consult your thermostat’s manual or contact your HVAC technician for advice. 

Aspect 5: Verify whether your Honeywell thermostat needs a reset after a battery change

Many Honeywell thermostats need a reset after you’ve replaced the batteries. And even if it is not required, the resetting of your thermostat might clear the fault which is causing the problem why your thermostat is not working.    

Resetting your thermostat takes it back to its default factory settings. Just remember that when you’ve done a factory reset you’ll have to re-program your thermostat again. 

As resetting your thermostat is not something you normally do very often, I’ll briefly give the steps to reset your Honeywell thermostat. 

  • Turn the HVAC circuit breaker off. If the thermostat has a separate circuit breaker or switch, turn that off as well.
  • Open the battery housing. (For some Honeywell thermostats you’ll have to remove the faceplate to get to the batteries, while others have a battery housing on the outside.)  
  • Remove the batteries.
  • Re-insert the batteries but place them backwards in the holder. (In other words, in the opposite orientation positions as indicated in the holder.) 
  • Keep the batteries in this backward orientation for five to 10 seconds.
  • Take the batteries out once more.
  • Re-install the batteries in the appropriate orientation and wait a few seconds. Your thermostat will display information on the LED screen when it is set for use.
  • Put the thermostat back onto the base.
Resetting honeywell thermostat after battery change

Aspect 6: Have you perhaps damaged the thermostat’s wiring during the replacement process?

Although some thermostat batteries are housed in an outside tray, most Honeywell thermostats require that you remove the thermostat from the base to reach the batteries. 

When the thermostat is being removed from the base, it is easy to unknowingly loosen one of the small wires. As these wires connect to the HVAC system and are the communication route between the thermostat and the HVAC devices, your thermostat will not work if the wires are not connected securely. 

To rectify this issue, reconnect and secure all the wires again.


The “easy” maintenance task of replacing the thermostat’s batteries can sometimes cause problems. Fortunately, the problems can normally easily be found and fixed. Keep a copy of this article in your thermostat’s manual for when you have to replace the batteries and run into some problems.


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