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Security & Fire Protection Systems/Kidde Smoke and Carbon Monoxide Alarm Lights


I have a Kidde Model KN-COSM-IB (actually 3 of them) and my question is that being hardwired the green light should be solid.  All three of the ( 2 October 2011, 1 Dec 2011) units green light blinks.  Therefor I believe it is only operating in DC Mode.  I have several other Kidde smoke detector units, installed in the house so I plugged on into where the combo unit is installed to see if the green light would be solid on the smoke detector only.  It does, so I believe the harness works and adequate power is being supplied.  Any suggestions why the light is not solid and blinking on the combo units.  I have had them in service for a couple of years and the only issue is I have to change the battery twice as often then the smoke detector only.  Just curious if the combo units are working correctly.  Thanks for your response

Hello Bill, and thanks for your question.

The green LED flashing indicates either an AC failure (and operating on battery only), or an alarm memory condition.

If you're sure that the units have AC power, try pressing the test/reset button on each detector. You should get a solid green LED after that.

Here's some text copied from the manual:

Green LED
The green LED will flash as described below under the following
Standby Condition (powered by AC and battery backup):
The LED will be constantly on.
Standby Condition (for model KN-COSM-IB only-powered
by only battery backup): The LED will flash every 30
Alarm Memory Condition: The LED will flash every
second during alarm. When the alarm condition goes
away, the originating alarm unit will flash the LED every
15 seconds until the test/reset button is pressed, thus
resetting the alarm. Note: to conserve battery power,
the Alarm Memory feature does not work when the unit
is in low battery condition.

If you don't have the manual, you can get it at this link:

I hope this helps!

Best Regards,


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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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