Vista 20P random alarm triggers


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Old 09-26-22, 09:26 PM
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Question Vista 20P random alarm triggers

I have a Vista 20P with all hard-wired sensors. In the last year, the alarm has been triggered several times by a garage door sensor. It is programmed for entry/exit. It is a sliding door, and the sensor is simply two parts that close the circuit when they get close. All the connections are solid. There is no rhyme or reason as to what sets it off, and I haven't been home when it has gone off, so I don't know if it did the delayed entry beeping before the alarm sounded. There were no wind events, or anything that I can think of that might have affected it. Since it only happens every few months, and I can't seem to reproduce it, I am baffled. I want to fix it because now I don't trust the alarm if I am gone for an extended period (like on vacation). Any ideas on what I should check?
 
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Old 09-27-22, 06:27 AM
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If you have a multimeter:
1. In the panel, disconnect one side of the garage door loop (terminal 8, 10, 12, 14, 15, 17, 18 or 20). Measure the resistance of the loop and post it here with the zone number that appears on the keypad.
2. Reconnect the wire you removed making sure that the plate under the screw clamps down on bare wire, not insulation. Give the wire a tug to make sure it is secure.

If you do not have a multimeter:
1. Arm the alarm with interior zones bypassed.
2. Open, close and lock the garage door. Wait for the Exit Time to expire.
3. With the door still locked, try to open it.
4. If entry reminder beeps do not start, pound on the door and frame near the sensor.


Otherwise, post a picture of the garage door sensor.
 
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Old 09-27-22, 06:39 PM
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Probably easiest just to replace the sensor (the most likely culprit) for an intermittent issue like this.
 
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Old 09-28-22, 06:03 PM
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Hi ThisOldMan,
I checked the circuit with a multimeter with the door closed, and it said 2.0K ohms. (I disconnected wire 18 because it is on zone 7.) There are two Honeywell 7945 sensors on the circuit wired in series. I went with these sensors because the gap can be 2.5", and I figured that would take care of any separation caused by wind, banging, etc. The sensors are 11 years old. I posted photos.

Not the best photos, but you get the idea.

 
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Old 09-28-22, 06:06 PM
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Hi sktn77a,
I probably will just end up replacing the sensors. They are 11 years old; I don't know if sensors have a service life. I was hoping to find a definitive problem so that I know it is corrected.
 
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Old 09-29-22, 07:57 AM
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Not familiar with that particular contact, but a contact's usual points of failure are the glass capsule surrounding the reed contact breaks from impact or they either blow open or weld shut from high current. I did have some magnets glued in position inside their case come loose and move out of position, but that was many years ago.

If you replace, there appears to be both Form A and a Form C contacts, so make sure you get the Form C which can be wired as a Form A.
 
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Old 10-05-22, 01:23 PM
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**update**

Yesterday I tried to arm the alarm, but it said the garage door was open, but the garage door was closed! Ha, finally caught the problem red-handed! I tried opening and closing the door, but the display didn't change -- it said the door was open. I disconnected the wire from terminal 18 (zone 7): when the multimeter bridged the disconnected wire to terminal 19, it showed 2k ohms (door closed), but when the multimeter bridged the disconnected wire back to terminal 18, it was infinity (open circuit, but the door was closed!). So I rewired the garage door to an unused zone (zone 2), and reprogrammed the zones. Now it seems to be working again. Does this mean that my Vista 20P board is going bad?
 
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Old 10-06-22, 04:23 AM
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Is the board bad? It's very possible.

However, when you read 2000 Ohms (wire to T19) you meter was set to read resisrance. Before you read between the wire and T19, did you change the function of the meter?

You're supposed to read resistance on a "dead" circuit (unpowered); the battery in the meter provides power. Any "outside" power interferes with the reading and can blow the fuse in the meter.

Set the meter to read resistance and hold the rest leads together. If it reads infinity the fuse is probably blown.
 
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Old 10-10-22, 03:25 PM
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Hi ThisOldMan,
I checked the meter and it is working fine. I am more concerned with the possibility of the board being bad. The garage door sensors seem to be working fine on the new zone. If one zone goes bad on a board, does that mean all the zones will go bad? Or is this just a fluke?
 
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Old 10-10-22, 05:53 PM
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Generally if you get a zone input failure, it means that the alarm control board is on borrowed time.
 
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Old 10-11-22, 07:34 AM
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If you resistor out the old zone (7?) and still get faults from that zone, then the board is definitely the problem.
 
 

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