What Happens If a Thermostat’s Battery Dies?

The thermostat batteries are of different forms. The common types include; 3V disc-style lithium batteries, AA and AAA alkaline batteries. The batteries used depend on the thermostat model. Batteries help store the thermostat programs so that the thermostat continues functioning normally in case of a power blackout and prevents the HVAC system from powering if there is a power blackout.

The thermostat batteries must be kept in an excellent state to increase their lifespan. Further, the batteries need to be changed at least twice a year to keep the thermostat working correctly. When thermostat batteries die, the thermostat will stop functioning unless the batteries are replaced with new ones. Once your thermostat battery starts dying, the thermostat begins failing slowly and finally stops.

What happens when the thermostat battery dies

what happens if thermostat battery dies
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Once the thermostat battery dies, the thermostat will stop functioning. The power supply to the thermostat will be disconnected automatically. After disconnecting, the thermostat will be unable to turn on unless you replace the battery.

Secondly, the thermostat will display a blank black screen as a sign that the battery has died. Finally, the units that perform heating and cooling stop functioning since there are no temperature commands to follow. Once all this happens, you will be required to replace the batteries to bring the thermostat back to normal functioning.

Low thermostat battery signs

Low thermostat battery signs

When the thermostat battery is decreasing, your thermostat starts changing. The signs of your thermostat low battery include;

1. Beeping of your thermostat battery indicator.

2. The air conditioning of the thermostat battery starts functioning abnormally or stops function.

3. Thermostat blank screen without any settings hence hindering you from making any changes on your thermostat.

4. Once the battery dies, the thermostat stops functioning.

Checking your thermostat battery

Checking your thermostat battery

Step 1: Open the thermostat menu

Using the thermostat ring, open the thermostat menu, and it will appear on your thermostat screen.

Step 2: Check the settings

Go to the settings and search for the tab that is indicated, the technical information. Press the table, and many options will appear. Look for the power setting tab.

Step 3: Click on the power option

Press the power button and check the number that is indicated battery.  View your thermostat battery level. If it is below 38v, your battery needs to be recharged or replaced, but if the battery is 38v and above, your thermostat battery is in good condition.

Steps on how to replace the thermostat battery

Firstly, make sure that the batteries you want to install are in good shape and not damaged. Ensure you charge the batteries used if they were implemented to be recharged.

Step 1: Remove the thermostat from the wall plate

Slowly detach the thermostat from the wall to which it was mounted. Carry the activity slowly so that the thermostat will not fall off and seriously damage.

Step 2: Check the thermostat batteries

Using a screwdriver, carefully unscrew the battery nuts. After unscrewing, check the battery slot for the old battery.

Step 3: Remove the old battery

Gently pull out the old battery from the battery slot. You can use the screwdriver to pull the battery out if held tightly in the battery slot.

Step 4: Reinstall the new battery into the battery slot

Carefully place the new battery in the battery slot. Ensure that the battery terminals are correctly identified and match the thermostat terminals as required while referring to the manufacturer’s manual.

Step 5: Return the thermostat battery cover to its position

After reinstalling the new battery, cover the battery slot with the battery cover. Ensure that the battery cover is tightly placed for the thermostat battery not to fall.

Step 6: Test the thermostat by turning it on

Try turning the thermostat to see if the battery was correctly placed. The thermostat should turn on. If the thermostat fails to turn on, recheck the batteries if they were correctly placed in the battery slot. Change the battery position and place it in the desired position. If the problem persists, check the battery state.

Step 7: Mount the thermostat back to the wall

Return the thermostat on the wall and screw it tightly to prevent it from falling off.

How to fix thermostat low battery

How to fix thermostat low battery

If your thermostat battery is running low, you will need to troubleshoot it to keep the thermostat performing its functions. Fixing the low battery thermostat requires you to follow the manufacturer’s instructions to avoid damaging the thermostat or the thermostat battery. The following are steps on how to troubleshoot your thermostat’s low battery.

Step 1: Check your battery status and then charge it until complete

Connect your thermostat to the power supply and switch on the socket. Leave it to charge until it is complete. Ensure that it does not overcharge because overcharging damages the battery and weakens it.

Step 2: Check for any wire damages on your thermostat and HVAC system

Inspect the wires of the thermostat to see if they have been correctly installed. If they are improperly connected, try to connect them properly while consulting a licensed electrician or the manufacturer’s manual guide.

Moreover, if the thermostat cables are correctly installed, proceed to check the HVAC control system cables. Try to connect them correctly. Test the thermostat if it is charging. Further problem persistence, an expert must be involved.

Step 3: Attempt using the C-wire cable instead of the power extender kit

If your thermostat allows you to use both the C-wire and the power extender kit method, try changing the process to see if the thermostat will connect. Try powering the thermostat to see if the battery is charging correctly. Ensure that you are careful to prevent damaging the battery.

Frequently asked questions about Thermostat’s Battery Dies:

  • What are signs of a poor thermostat that require battery replacement?

The signs of a poor thermostat include:

1. The thermostat does not show any power. Poor thermostat battery hinders power supply to the thermostat. Therefore, the thermostat fails to detect any power being supplied hence does not turn on.

2. AC fails to switch on. If your AC does not respond to power presence, it shows that your thermostat battery is dying and requires replacement. Once the reserves have been done, your AC will turn on.

3. AC fails to turn off. Your ac may run continuously and fail to detect turn off even after turning it off. Therefore, you will be required to remove the old battery from the thermostat and replace it with a new battery. Your AC will respond when turning on and off.

4. Incorrect temperature reading. Poor battery tempers with the temperature readings of a specific room. Once the temperatures are tampered with, it will be challenging to get accurate temperature readings unless the battery is replaced and the thermostat is set correctly.

  • Why is my thermostat not working?

Step 1: Inspect your thermostat for any defaults

Check if your thermostat battery is correctly installed and has 38v and above power. Inspect the wires of your thermostat if they have been correctly installed.

Step 2: Check for any dust on the thermostat wires

Scrutinize your wires to see if dirt has accumulated on them. Try cleaning the cables and even the thermostat using a clean cloth while following the manufacturer’s instructions. Use a compressed air system where necessary to blow away the dust.

Step 3: Inspect the wires and replace the damaged cables

Wires may corrode when connected to too much power. You will be required to replace the cables for your thermostat to work effectively.


The thermostat requires battery replacement once per year to improve the efficiency of the thermostat. Replacing the battery requires simple procedures. Both professionals and non-professional can use the information above to replace and fix the thermostat batteries.

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