Hi all. I have a 20 year old Woods freezer that I clean out yearly. Last time I "manually" defrosted it, and refilled it with food and brought it down to Zero, the alarm didn't work. I decided to just check it every day to make sure it hadn't quit. Well, one day, months later, when it was fuller, I realized that the alarm still worked. Is it possible that it has to be filled to a certain level, for the alarm to work? Thanks.