Electronic Alarms and Home Security Devices - Repairing faulty zone

One of the zones on my security system appears open. There are seven 1/4" recessed sensors with magnets on windows. Questions: 1. How do you check "continuity?" Do you use a meter or do you cut the wires and touch them together? 2. What is the best method to attach new sensors? Do you use shrink tubing or just tape? 3. Do sensors "break"? (They are 18 years old. Thanks, Tom

I purchased a digital multimeter from Radio Shack. I placed one lead on the sensor and the other sensor on the magnet, but the short isn't showing on the meter. Is there a better method of testing the short?

Door and window contacts are just a normally closed switch. When then magnet is next to them, you should see a continuity between the two leads of any individual switch, it should open if the magnet is removed.

They can and do fail (they are a reed switch smaller than a pencil lead). They are not difficult to replace, the best method is to use a "B" connector or similar device. You do _not_ want to just "twist and tape". It _will_ fail.

If your zone wiring is individually run back to the the panel location, that's the best place to check them. The bad ones are the ones that show an open when the magnet is in proximity.