Home smoke detector problem

Smoke Detectors: Home smoke detector problem

Electrical Smoke-detectors Question:
Some of our smoke detectors have lost AC power. I've tried looking for loose connections in adjacent detectors and close-by receptical/switch boxes, but have found none. Are these all on the same circuit? If so, then the power lines would go from the 'first' to the 'last' in the house, and so my problem would have to be between the last working one and the first non-working one? Any idea how to figure out what's up?
Thanks, Brian.

Hi Brian, Great Question!
If you have interconnected smoke detectors, which would be indicated by the third wire, typically yellow, then all of the smoke detectors should be powered by a common feed. It is very common that this circuit be an existing lighting circuit so that in the event of a power loss it would be noticeable. You are correct to inspect each smoke detector junction box and look for a loose connection

Be aware that these detectors do go bad also, so the voltage at each j-box should be verified. You could swap bad detectors with known good ones to test as well. If the home has been remodeled and new smoke detectors were added it is possible that they are not interconnected, although that would be rare and not recommended anyway. Let me know if this helps.
Dave Rongey, Licensed Electrical Contractor