It has lost its ac power.

Is that what happens when you close the door?
Do they "go bad"?

No, if you have ac power and, a dead or no battery, the alarm will beep. If you have a good battery and no ac power the alarm will beep. If it starts beeping when you put the battery in, then the battery is good and the ac power is missing. I don't know how you got that I was saying that something was going bad when the door was closed.

Remove rthe entire detector and its base plate and check the AC power wiring in the box behind the unit.

You need to turn off the circuit that power it before messing around.

This can be a chore if the unit is not connected and they are not all on the same circuit.

But to answer your question: "Do they go bad?" The answer is "yes, they do". They last about 10 years.

I would take the battery out and test that first.

The original poster must have met their demise in an attempt to correct the problem with their smoke alarms. Exactly the hazards that causes me to hesitate in giving such advise to the unqualified, otherwise they would have surely offered a thank you for timely, free, and spot on advise to remedy their problem.

Or maybe he just has not had the time to follow up. I travel a lot and have not been able to follow up>

"thank you". Are you sure I am unqualified? Just because I ask a question doest that make me unqualified? Is this not why we all joined this forum? If you asked me for directions while driving does that make you unqualified to drive? Sorry, I just can't stand negative comments!

Honestly I understand where both of you are coming from. Take this into conisderation though when you ask a question on this board.....speaking for myself only (the same prob. holds true for others though)I've worked very hard at a job that can be very physically and mentally demanding ,at times, for many years as well as done schooling after a full days work without the benefit of any school loans available for my line of work. When you ask a question I answer it out of the experience that I've gained through a lot of hard work. The experience and knowledge I've gained makes me able to make a living at what I do so when I give out hard earned advice to someone who maybe hasnt done so, its almost like taking food from me and my familys mouth. Thats all. Just remember when you do any electrical work, electricity causes fires, serious injuries, and death

I completely understand where you are coming from. I own a low voltage company in Florida. I have done all the school need to be very successful. I give plenty of advice to customers and never think twice about it. I have built my success on customer service, the one thing you hardly ever get anymore. Like I said, I can not stand negative comments. It would have been better to ask "what was the out come?".. I am done. I will be more selective with my questions on this forum.

So the only thing I got wrong was when I said you met your demise.

"I own a low voltage company in Florida. I have done all the school need to be very successful."

That still leaves you unqualified to work on 120v systems.

"I have built my success on customer service, the one thing you hardly ever get anymore."

Your actions belie your smug entitled character, and I am not the only one that will notice. I was ready to give you some advice here related to customers, but you really don't need it.

Lastly your driving analogy isn't relative as not only do I have a drivers license, I also have an electrical license.

"Thank you"

You are welcome.