Struggling with a hard-wired, interconnected smoke detector that seems
to be chirping in response to humidity (we're having a cold summer in
Minnesota). I tried replacing the battery, blowing everything clean
with a blow dryer set on cool, and replacing the removable unit itself.
Nothing helped. And here's the really hard part which has even the
electricians (including the company that installed it) stumped. The
chirping is not coming from the removable part. It's coming from the
wiring up in the ceiling. I know this for sure because I took the
removable part out of the house and put it in the garage. The ceiling
hole kept right on chirping.

How is that possible?

I need to know because I want to pull the hard-wired system and replace
it with battery-only detectors. With battery-only, there IS NO wiring
inside a hole. If the detector starts chirping from humidity (and we
have a lot of humidity in MInnesota), you can remove it from the ceiling
or wall and stick it in the garage until things dry out and there won't
be anything left in a hole in the wall or ceiling to go right on
chirping. But the electrician I called seems to think if he just
removes the removable part and covers the hole with a plate, he'll be
done. He doesn't believe the chirping is coming from the hole, not the
removable part.


I had a similar problem with a customer's smoke detector a few months ago.
They called and said the smoke detector was chirping. They changed the
battery, but the chirping did not stop. I go over there with three new
smoke detectors figuring if one was bad they are all probably ready to be
changed. I changed them, got paid and left. They called me a few hours
later and said it was still chirping. I went back over and sure enough I
heard the new one chirping. I get up on the ladder and disconnected the
wiring, take it down and pulled out the battery backup. I then pressed the
test button for a minute to reset the unit. As I was getting ready to
reinstall the new detector I heard a chirp. I waited and heard it again.
It was coming from a carbon monoxide detector that was located behind the TV
and plugged into the wall. Its battery was due for replacement.

I'm thinking that you have a similar problem. The chirping is probably
coming from something else. The fact that it happens only at night makes me
think that you might have a cricket or some other little critter around in
the ceiling or wall.