alarm system goes off every year during vacation
Hi! I have a DSC PC1500 alarm system that for the past three years has triggered a false alarm while I was away on vacation. It's always zone 4 (bedrooms) which have 2 motion detectors on it and nothing else. When I called my installer (an independent guy who works on his own) three years ago, he said he opened the motion detector cover in the master bed and found a spider inside the housing, and attributed it to that. Last year, it went off again during my vacation, and he attributed it to the backup battery being bad intermittently (which my electromechanics background makes me doubt very seriously). This year, he says it's my battery again. When I asked him if the sensors themselves could be at fault, he said just because when he waves his hand at them the little green light goes on, they can't be bad!
That being said, I wanted to do my own diagnostics, so I removed the mouldings that hide the wiring to inspect it, and everything is fine visually. An ohm test proved negative as well, and all the connexions are clean and tight.
Since there seems to be only two possibilities (bad motion sensors or bad control board), please help me know a bit more about motion sensors.
First, do these sensors have a limited life like smoke detectors? If so, what's the average life of such sensors? Is it better to have the same brand sensors and main panel? I have one "no name" sensor and a paragon sensor on zone 4. Could excessive heat buildup in the house have triggered one or both sensors? Finally, zone 4 is the zone with the longest wiring run (around 50 ft); could that be too long? The wiring does not come close to any power cables.
Finally, while I don't think it's very likely, can the DSC control boards fail in the way that I describe? The system was purchased in 1998 if that matters, but the motion sensors on zone 4 were replaced in 2004.
Can you please help me answer some of my questions and help me troubleshoot my system? Any help would be appreciated. Thanks.