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What’s the deal with a low battery in a thermostat? Most people have this question. Does a low battery affect how your thermostat operates?
Occasionally, you may notice that your thermostat isn’t operating as efficiently as it should be. It could be because of a low battery. If you’re a homeowner, knowing if this happens and when your thermostat runs low on battery will help you know what you should do next to fix the problem.
A low battery on the thermostat can affect how your thermostat operates. However, this can depend on the type of thermostat you have. A low battery may not affect how it works if you have a digital thermostat with a c-wire connection. But if you have a thermostat without a c-wire connection, a low battery will probably affect how it works
Can a low battery in a thermostat affect how it operates?
The answer to this question will depend on two things.
1. Your thermostat has a C-wire
2. Thermostat is not powered by a C-wire
The above two factors can determine whether or not a low battery can affect the regular operation of your thermostat. Let’s dive into more detail about each of these two factors.
Thermostat with a C-wire
A thermostat that has a common wire (also known as a c-wire) will not be affected by low batteries. The c-wire supplies 24 volts from the transfer to your thermostat, so when the batteries are low, they should not affect how it works.
So, what is the purpose of batteries in a thermostat with a c-wire? The purpose of batteries in a thermostat that has a common wire is to help it return the memory or the settings after a power outage. Apart from that, batteries on a thermostat with a c-wire don’t play a big role.
When your battery dies in your ‘c-wire’ thermostat, you will only be inconvenienced when you experience an outage because your settings will be lost.
Thermostat without a c-wire
Unlike a ‘c-wire’ thermostat, a thermostat without a c-wire or 24-volts power from the transformer will be affected by the low battery. That is because their thermostat has no other power source besides the batteries.
So, a dead or low battery on this knight of thermostat will prevent your thermostat from working as it should. So yes, a low battery will affect how a non ‘c-wire’ thermostat will operate.
Symptoms Of A Low Battery On A Thermostat
Now, how will you know when your thermostat battery is running low? You don’t want to suddenly be disrupted from enjoying your heating or cooling. So you will always want to replace your batteries when they are about to go low.
Here are some signs to tell you that your thermostat batteries are about to go low.
1) Display blinking low battery message on the thermostat.
Batteries can last for about 8-12 months on most thermostats. And most of them are designed to give you a warning about 2-3 months before they completely die out. They will flash or display a ‘low’ battery warning during this period.
When you notice the message, consider replacing the batteries to avoid being inconvenienced when they completely die out.
2) Faint thermostat display
A faint thermostat display is also another common symptom of low thermostat batteries. Usually, when the batteries are low, you won’t easily see the display on your thermostat screen due to their faint appearance indicating a weaker power supply by your batteries.
3) Thermostat display goes completely blank
When your thermostat batteries completely die out, the screen can go blank. But it should also be noted that you can have a blank screen on your thermostat when the battery contacts are corroded.
4) Equipment not responding or taking long to respond.
Have you tried using your thermostat, and the equipment is simply taking a long tor not respond to temperature adjustments on your thermostat? That could indicate that your thermostat batteries could be low or about to die. A replacement of the batteries should resolve this issue.
Can a thermostat work without batteries?
Yes, it is possible for a thermostat to work without batteries. That is, for those thermostats supplied with 24 volts from the transformer by the common wire.
However, it should be noted that when there is a power outage, the settings will not be retained when the batteries are either dead or not present.
But thermostats that do not have a c-wire connection will probably not work without batteries. So, for these thermostats. You’ll want to ensure that your batteries remain sufficiently charged (for the rechargeables).
How do you change the battery on a thermostat?
Replacing thermostat batteries is not a difficult task to undertake. For most thermostats, you’ll need a flathead screwdriver to detach the thermostat housing from the wall mounting plate. While for others, you may simply need to pull off the thermostat’s face from the wall.
But every model can have its own way of doing things. Kindly refer to your user manual for specific instructions. Anyway, here are some of the general steps that can help you replace your thermostat batteries.
1) Honeywell Thermostats Battery Replacement
This applies to most Honeywell models.
Step 1. Ensure that you already have batteries on hand so that your thermostat programming can be retained if the replacement is done within 2 minutes.
Step 2. Remove the battery compartment from the Honeywell thermostat (typically from the right side and pop out the two AA batteries with your flathead screwdriver.
Step 3. Replace the old batteries with the new ones and plug back the battery compartment into the wall thermostat housing.
2) Vivint Thermostat Battery Replacement
To replace batteries on most Vivint thermostats, follow these general steps:
Step 1. Remove the thermostat from the mounting plate by pulling it towards you.
Step 2. Pop out the old batteries and replace them with the new ones (note that Vivint thermostats typically have four batteries in them.) Before adding new batteries, wait at least 30 seconds.
Step 3. When you are done replacing your batteries, remount the thermostat into the mounting plate
That’s it; you are good to go!
3) Nest Thermostat Battery Replacement
To replace batteries on your nest, follow these easy steps.
Step 1. Pull the thermostat from the wall, revealing the two AAA batteries on the thermostat.
Step 2. Ensure negative goes on the negative, positive on positive terminals
Step 3. Replace the old batteries with new ones
Step 4. Now put the thermostat back into the wall plate, and that’s it; you are done.
When To Change Batteries On a Thermostat?
Changing batteries on your thermostat should be immediately after you notice they are running low. This will prevent unnecessary inconveniences that can come with a sudden loss of battery power.
You can also replace your batteries when the display flashes a warning ‘low’ battery message.
In general, batteries can last up to 1 year, so you can make it your routing to replace batteries anywhere from 8-12 months to avoid the risk of them dying out before replacement.
My thermostat doesn’t work after replacing the batteries, why?
There could be a few reasons why your thermostat doesn’t work after replacing the old batteries with new ones. The following are the possible causes and solutions to each.
1. Thermostat screen is still blank. If the thermostat’s screen is blank after replacing batteries, there could be issues with your thermostat battery contacts; most likely, they are corroded and need a bit of cleaning. You can use sandpaper or any material that is a little bit rough but not too aggressive for cleaning.
2. Thermostat not cooling on cool and not heating on heat: Problems with heating/cooling could indicate a bad thermostat wiring. If you have a user manual for your thermostat, use it to verify that the wiring was correctly done and rectify anything wrong.
Other times, the loose wire could be the culprit for your thermostat malfunctioning. Try tightening up anything loose.
Types Of Batteries Used In Thermostats
The commonly used batteries in a thermostat are the AA( double As) and the AAA( triple As) Alkaline batteries.
Other batteries that are used include the 3V disc-style lithium batteries.
- Plastic, Metal
- IN THE BOX: 4-pack of CR2032 3 volt lithium coin cell batteries; replacement for BR2032, DL2032, and ECR2032
- DEVICE COMPATIBLE: Ideal for watches, calculators, key fobs, Apple TV remotes, and other small electronics
- DESIGNED TO LAST: 8-year leak-free shelf life
Replacement of old batteries with newer ones will ensure that your system retains the settings or your thermostat’s programming. Apart from that, this will keep your thermostat working efficiently.
To conclude, we have learned that there are types of thermostats that could be affected by a low battery, and others are not. We have also seen symptoms when your thermostat batteries are running low.
In other words, most digital thermostats with a c-wire work fine even when their batteries run low. Their operation can mostly be affected when there is an outage. Nevertheless, getting new batteries is still necessary to avoid losing your settings in these instances.
We hope this has been helpful. Thanks for reading.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.