Can cold weather affect a home alarm system?
December 9, 2009 11:11 PM   Subscribe

Can cold weather affect a home alarm system?

We're experiencing unusual cold weather here in the SF Bay Area. Early yesterday morning around 5am, I was rudely awakened by my home alarm system. I checked the tripped alarm, which was a garage access door from my backyard, but the door was securely locked and deadbolted.

The alarm sensor is embedded in the wooden door jamb, so i'm wondering if it's possible that the cold weather could have caused it to trip, maybe from thermal expansion or something? Something to add, the temperature here is in the mid-40's, however, I am unable to arm the system because it shows that the faulty alarm is still tripped, though the door is securely locked and deadbolted.

If not, what do you suppose could be the explanation?
posted by beammeup4 to Home & Garden (5 answers total)
What kind of sensor is it?
posted by flabdablet at 11:20 PM on December 9, 2009

What about a power interruption? We've had cold weather here in LA, and have had a few power outages.

Hubby says his office lost power because people were plugging in heaters on low amp circuits. Took 4 hours to get someone there to fix it. Sigh.
posted by Jinx of the 2nd Law at 11:23 PM on December 9, 2009

It's probably a magnetic reed switch. Try taking a strong magnet and putting it next to the sensor in the door jam and see if the alarm thinks the door is closed. If it does then the magnet in the door is probably just too weak; perhaps it fell out of alignment and is too far away from the reed switch to activate it. You might be able to adjust the clearance if there are screws that you can loosen.

As far as the temperature goes, I don't think that 40s is low enough to do anything, so it's probably just coincidence.
posted by Rhomboid at 12:18 AM on December 10, 2009

Is it a ball switch? Magnetic switch?
Either there's a "cold" solder joint on the switch in the door jamb, the door contracted with the weather and the switch isn't lined up with the magnet in the door. If the circuit closes when it gets warmer it's one of these usually.
posted by jara1953 at 3:37 AM on December 10, 2009

I had the opposite early this summer. On successive hot days the alarm tripped just before noon, when the sun had been beating down on the door for a couple of hours (and presumably expanding/warping it enough to break the magnetic switch's contact). The guy from the alarm company came out and realigned the switch, and it hasn't been a problem since.
posted by hangashore at 5:48 AM on December 10, 2009

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