Check the date on the replacement alarm...
If you have the alarm replaced you may want to check the date on the replacement. While our SunSeeker was in 'drydock' we asked them to swap out the alarm, which was dated 2005. The motor home is a 2006 model, so the alarm was probably original.
Anyway, the date on the replacement was 2010 or 2011 which, given a five-year lifetime, would mean replacement pretty much, now. They swapped it for a brand-new alarm, dated Dec 2015.
As an aside, our carbon monoxide alarm is mounted in the bedroom, and doubled as a low-battery alarm. On our first shakedown we woke up to the thing going off at dawn. Turned out the house battery became depleted in the night. That's when we found out the generator didn't work, so we had to run the truck engine for a couple of hours to recharge.
2006 Sunseeker 3100SS - "Heart Of Gold"
2006 RAM 2500 Cummins
2006 5th Wheel - "Escape Pod"