optima xm alarm keeps going off during the night even though its not been set,this has only happened since i dusted two of the sensors but they dont appear to be loose

s a betts, August 2010

Right you have not as most others do is read the keypad.
What did the keypad say before/after you entered your code to silence it?

At a guess you may have knocked a cover just enough to cause a tamper. Reading the keypad will give an indication of which zone ( if it is that of course) is affected.

Alarm, August 2010