....... I still switch battery and its still doing sound. What else can be going on?

 

Had the same problem with a unit at my daughter's house. B/U battery quit and it beeped. Changed battery and it still beeped. After holding down the test button for a few seconds, not just a quick push, it went through some sort of reset sequence and was then silent.

After class I'm going test by burning paper to make sure it works, then going read manual and look on the exp date. I did write on the backside (part on ceiling) the date I bought it so that will help me out as well.

If you don't know exactly how old it is then the odds are it is at least 5 years. Buy a new one.

After class I'm going test by burning paper to make sure it works, then going read manual and look on the exp date. I did write on the backside (part on ceiling) the date I bought it so that will help me out as well.

 

For what its worth why not just spend the $20-30 and get a new one? If you can find the same manufacturer more than likely it will use the same pin connector. No hassle of turning off breakers just unplug the old and plug in th new. Even if you have to replace the wire harnass.. Secure the power at the breaker for the detectors, and remove old harnass from wire nuts and twist in the new ones.