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Smoke alarm constantly flashing red

Guest Beth

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I have two 660 MBX smoke alarms (battery and mains operated). Manufacturing date is 2015. One went off randomly so I pressed hush button. Have cleaned and changed batteries, but as soon as I put a battery in the one that originally went off, it goes off again and will only stop if press hush button. It also constantly flashes red (every second).  When I connect to mains the green lights show on both alarms, but the red light constantly flashes and the alarm goes off. Any ideas why it is doing this or what to do?

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Hi Beth

The red light flashing every second, even when the alarm is silenced, indicates that it thinks there is smoke present at all times. As you say they have been vacuumed so it shouldn’t be a dust problem. That leaves two possibilities:


1.    The alarm was installed in or too close to the wrong type of room, like a kitchen or garage, and the sensor has been contaminated by fumes and residues that a vacuum cleaner won’t remove.

2.    The alarm is simply faulty and will need replacing under warranty.


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  • 1 year later...
Guest Adriana

The smoke alarm in my room is hard wired 

the red lights are continuously flashing until it makes a clicking noise, then it stops. Then the clicking noise happens again and it starts again 


is this normal?

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  • 2 months later...
  • 3 months later...
10 hours ago, Guest Lynn said:

Hi have two new fire detectors put in one hall way which flashes red all the time is this normal

Most smoke alarms do flash on a regular basis to indicate they are powered and working, I would have to ask, what do the instructions for your smoke alarm say?

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