Skip to Content

Smoke Alarm Blinking Red After Changing Battery: What to Do?

Sometimes it’s seen that after we’ve changed low, old, or faulty smoke alarm batteries with new ones, the smoke alarm is still blinking red which can be a concerning issue.

So as a holder of a smoke alarm, you would be concerned enough to know why your smoke alarm is blinking red and what should you do in this situation. Let’s read ahead to know the explanations and solutions to this query.

Smoke Alarm Blinking Red After Changing Battery

After changing the battery, a smoke detector blinks red when the smoke detector is faulty or an old one that needs to be replaced to solve this issue. Also, if the battery is faulty, incompatible, or isn’t installed correctly, a smoke detector surely will blink red even after the battery is changed.

As several reasons are responsible for causing a smoke detector to blink red even after the old or faulty batteries have been replaced with new ones, anyone needs to know the reasons and the solution to the problems.

Thus, the main causes are described below with their correct solutions for your knowledge. 

Old Smoke Detector: 

As per the U.S. Fire Administration, the average lifespan of a smoke detector is about 8-10 years. After passing 8-10 years of using a smoke detector, it’s essential to replace it with a new one as the sensors become less accurate on older units.

As a result, with weak sensors, the smoke detector is caused to blink red even after you have changed the battery. 


Changing the whole smoke detector device with a new one is the only solution that can solve the problem of your old device blinking red after putting back new batteries.

Especially if you are replacing batteries twice a year and if it still blinks red with the new battery in it. Then it’s clearly indicating that it’s time to change the old smoke detector. 

Faulty Smoke Detector: 

The smoke detector is an electronic device after all, so it can go faulty after all these years of using it. And a defective smoke detector can cause problems like blinking red even if you have switched to the new battery. 


The solution to a faulty smoke detector is the same as an old smoke detector, you need to change the whole device, not just the batteries.

So if your smoke detector is showing signs of being faulty and is blinking red after restoring the battery, get a new smoke alarm. 

Incompatible Battery:

If you have mistakenly replaced the old battery with the new but incompatible battery, your smoke detector will flash red light. Even worse, it can end up damaging the device too. 


Using a compatible battery is the solution to this problem. So always do a double check before changing the old battery, and if you are unsure, contact the manufacturer and be sure to use the compatible battery. 

Improperly Installed Battery: 

If your smoke detector needs a pair of batteries, while putting back the new ones, they must be installed in the right way in their respective spots.

This means the batteries should maintain their correct negative and positive position inside the battery compartment. If they are facing the wrong side, obviously the smoke alarm will not be working and will keep flashing red light. 


You must install the batteries correctly by checking the positive and negative sides of the batteries and the battery compartment to make the smoke alarm function in the right manner, and not blink red after having a battery replacement. 

Old Battery: 

Smoke detector batteries come with a shelf life of about 6-10 months approximately. After this period, the batteries become old or faulty.

While replacing the battery in your smoke alarm, if you have put back a battery that has passed the expiry date, the smoke alarm will not be activated again to work properly, and it will continue blinking red. 


Check the expiry date of the battery before putting them in the smoke alarm so that you can know if the battery is still suitable to be used or not. As long as the smoke alarm is working fine, it should make the device stop blinking red.

Should A Smoke Detector Blink Red After Battery Change?

As long as the smoke detector is not a defective one or you are using the compatible and fresh battery in the right direction inside the battery tray, the device should not blink red after the old battery has been switched with the new battery. 

However, if you are using an electric-powered smoke detector that comes with battery support, it might blink red and chirp to be error free after the battery is replaced and the smoke detector is reset.

It’s a sign to let you know that the smoke detector is functioning well after a battery swap. Rest assured that it’s nothing to worry to be worried about. 

In case, the blinking red light is still or it’s not stopping after a battery change, it certainly can be an issue to be tensed about. In that case, talk to the manufacturer or call a professional to find out the root problem to fix it. 

How Do You Reset The Red Light On A Smoke Detector?

After changing the battery of a smoke detector, the device is required to be reset so that the battery can get connected to the smoke alarm again and it will reset the red light automatically too. 

Since both battery-powered and electric-powered smoke alarm with battery backup is now available, here the steps to reset both types of the smoke detector to reset the red light have been explained.

Battery-Powered Smoke Detector 

Remove The Battery: 

First, you will be needing to take out the old batteries to reset both the smoke alarm and the red light.

Take out the outer casing and find the battery tray, and then you will find a lever, pop the lever to open the battery tray. After that, remove the old battery from the smoke detector.

Press And Hold The Test Button:

Then, press and hold your device’s test button for about 5-15 seconds, until you hear a beeping sound. 

Replace The Battery: 

After that, insert the new battery in the smoke detector and do the resetting again by pressing and holding the test button for 15 seconds.

You will again hear a beep sound once which means your inserted battery is connected to the device and the red light will be reset too. 

Electric-Powered Smoke Detector With Battery  Backup 

Turn Off The Main Breaker: 

Since an electric-powered smoke alarm with a battery back runs by getting electrical power, turn off the main breaker of your house to stop the running electrical current in your smoke alarm.

Turning off the main breaker will prevent all potential electrical dangers that can be caused to you. 

Take Down Smoke Breaker: 

Next, take the mounted smoke alarm down from your ceiling and plug out the powered cable connected to the smoke detector.

Press And Hold The Test Button:

Remove the old/faulty batteries from the smoke detector, then for 15 seconds press the test button of the smoke detector. You will listen to a beep sound.

Insert New Battery And Reset The Device Again: 

Now, replace the battery in your smoke detector, then connect the power cable to the device again, and mount the device back to the mounting bracket on your ceiling.

Lastly, turn on the main breaker and you will hear a beep sound again, which means the power is restored and the smoke alarm and the red light are reset.

Sometimes, red light can blink accompanied by the beep sound after turning on the breaker, which is normal. 

How Do I Turn Off Low Battery Smoke Detector?

To turn off a smoke detector with a low battery issue, press and hold the test button on the device for 15 seconds or until the smoke alarm stops beeping (beeping is a sign of low battery).

If the smoke alarm continues to beep, take it down from the ceiling and unclip all connected wires. After that, open the battery cover and take the battery out of the smoke alarm and the device will be turned off instantly. 

And if you are using an electric-powered smoke detector with a battery backup, the procedure of turning off a low battery smoke detector will be the same, but you need to turn off the main breaker in your home.

Final Thoughts 

An old/faulty smoke detector will blink red even after the old battery is replaced with the new battery. Besides, faulty or old batteries, incompatible batteries, and improperly installed batteries can also cause a smoke detector to blink red after having a battery change.