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Resolved * Wired Magnetic Door Alarm Surface Contact

sep8001

Well-known Member
Hi

It seem as though our Wired Magnetic Door Alarm Surface Contact may be dying. Not sure how these work but over the last few weeks when we come into the house the alarm goes off becuase the wall sensor is picking up movement and does not allow us time to key in the number on the key pad.

What I have noticed is that it only happens if the door sensors do not bleep when we open the door on our way out once we have set the alarm.

If it is the door sensors that have become faulty is okay for me to change them or do I need to get the alarm man in to do it. The door sensors are only a few quid at screwfix. Also if I do decide to change it myself I presume as long as I get the wiring correct it should be okay and I will not have to get the whole alarm reset.

Thank you
 

nheather

Distinguished Member
They are usually a magnet and a reed switch. When the door is closed the magnet is close to the reed switch and contacts close. As the door is opened the reed switch is moved away from the magnet and the contacts open.

My concern is that these very rarely fail - there isn't really much to them and if they did fail it would be in a state equaivalent to the door being open (contacts open) which I would have thought would stop the alarm from being armed.

As to your question - if it is a faulty reed switch or magnet it is pretty easy to fix yourself.

Cheers,

Nigel
 

sep8001

Well-known Member
Hi Nigel,
Thanks for the reply. It may just be a loose contact due to door slamming or water damage as we sometimes get water coming in when it rains heavily.

Might just check the contacts first to see if they are loose.

Thank you for explaining how they work.

Kev
 

wilbanat

Distinguished Member
They can a do fail often, and can stick open of closed. If it is a simple alarm system you should be able to do it yourself. If it is a fairly new system then is could possibly be a resisted circuit..2k2 4k7 or 1k 2k etc. An old standard double pole contact will have (normally) 2 silver screws and spare brass screws. The silver are the reed switch, so the alarm circuit pair go to them and the tamper pair to the silver one. This is what it looks like inside

And this is a standard contact
 
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Doug the D

Distinguished Member
Just to add to the other 2 helpful posts, I see these reeds on the doors of street cabinets that I work on, and now and then I do have to replace them. I've noticed that the magnetic reed as shown in @wilbanat's post is actually encased in thin glass or plastic. If this casing has been damaged (possibly by a teenager-strop door slam), then it's a very simple fix.
 

sep8001

Well-known Member
Thanks, had a quick look and it looks okay. Just tightened the screws and will wait till the weekend to see if it is okay. If not will try and change them.

This is what they look like.

ImageUploadedByTapatalk1421083346.082993.jpg


Thank you all for the help.
 

wilbanat

Distinguished Member
Thanks, had a quick look and it looks okay. Just tightened the screws and will wait till the weekend to see if it is okay. If not will try and change them.

This is what they look like.

View attachment 547171

Thank you all for the help.
Quite old but looks very standard. As long as you don't have a monitored alarm that requires an engineer reset in the event of a tamper, you should have no problem changing that.
 

sep8001

Well-known Member
Thanks, the alarm is about 8 years old and calls my mobile if the alarm goes off. I can stop it sounding with a key press on the phone.

Earlier when it was not working the O.H tapped it a bit and it started working. I have opened it and tightened the screws and will see if it goes off again.
 

wilbanat

Distinguished Member
Thanks, the alarm is about 8 years old and calls my mobile if the alarm goes off. I can stop it sounding with a key press on the phone.

Earlier when it was not working the O.H tapped it a bit and it started working. I have opened it and tightened the screws and will see if it goes off again.
Just sounds like it's getting stuck 'closed' more than likely you will have a wire pair on the 2 silver screws and if they bothered with a tamper, then there will be another wire pair twisted together under a brass screw. If it looks different to that when you take it off then you are welcome to massage me and I will try and help.
 

spyder viewer

Well-known Member
Be nice if you could post how you solved the problem.
Reed relays can fail by the contacts sticking in the closed state. That would explain your not getting a "beep" on entry/exit.
 

sep8001

Well-known Member
Be nice if you could post how you solved the problem.
Reed relays can fail by the contacts sticking in the closed state. That would explain your not getting a "beep" on entry/exit.
Hi

I bought replacements from amazon and swapped them.

Initially I was worried that I would not be able to connect the wired part of the connectors, but PM from @wilbanat with support and help if I got stuck gave me the courage to try.
 

wilbanat

Distinguished Member
Be nice if you could post how you solved the problem.
Reed relays can fail by the contacts sticking in the closed state. That would explain your not getting a "beep" on entry/exit.
The reed was sticking closed, yes. Luckily it was a conventional alarm system, so replacing was pretty straight forward for the op, no resistors involved. :smashin:
 

Eagleboy

Novice Member
They can a do fail often, and can stick open of closed. If it is a simple alarm system you should be able to do it yourself. If it is a fairly new system then is could possibly be a resisted circuit..2k2 4k7 or 1k 2k etc. An old standard double pole contact will have (normally) 2 silver screws and spare brass screws. The silver are the reed switch, so the alarm circuit pair go to them and the tamper pair to the silver one. This is what it looks like inside

And this is a standard contact
Having similar problems. My alarm system is about 9 years old and have a similar switch to the photo sent by the member. The alarm control panel is showing that the front door circuit is open when the door is closed. Will I need to shut the power off to change the switch? Thanks
 
Last edited by a moderator:

sep8001

Well-known Member
Having similar problems. My alarm system is about 9 years old and have a similar switch to the photo sent by the member. The alarm control panel is showing that the front door circuit is open when the door is closed. Will I need to shut the power off to change the switch? Thanks
Hi

Not sure if all alarms are different, but from memory on my one as it was disarmed it was just a simple swap.
 

Eagleboy

Novice Member
Hi

Not sure if all alarms are different, but from memory on my one as it was disarmed it was just a simple swap.
That’s what I suspected. My only concern was the ‘tamper’ wiring and disconnecting this would trigger the alarm?
 

Eagleboy

Novice Member
That’s what I suspected. My only concern was the ‘tamper’ wiring and disconnecting this would trigger the alarm?
 

IronGiant

Moderator
So long as the circuit isn't broken ie the two wires at the switch end stay twisted together it shouldn't trigger. Would the alarm actually trigger if tampered with while disarmed anyway?
 

Eagleboy

Novice Member
Ah, that's true! I've checked the wiring and it's all intact on the switch. I've also listened for an audible 'click' to see if the switch is operating when the door is opened and closed and there was nothing. So I've assumed the switch is faulty and have ordered a new one. Thanks for all your comments!
 

bdolph

Novice Member
Many reed type alarm sensors have a rhodium coating to help the reeds from sticking together. Two big culprits for sticking is, not being activated in a long time and stray voltage surges from lightning (which can actually weld the reeds together). If you temporarily remove the sensor wires and short them to test that the actual alarm circuit is work and this checks out ok, then replace the alarm contact. They are pretty inexpensive. Pay attention to magnetic polarity instructions as some sensors are more sensitive to this than others.
 

Eagleboy

Novice Member
Many reed type alarm sensors have a rhodium coating to help the reeds from sticking together. Two big culprits for sticking is, not being activated in a long time and stray voltage surges from lightning (which can actually weld the reeds together). If you temporarily remove the sensor wires and short them to test that the actual alarm circuit is work and this checks out ok, then replace the alarm contact. They are pretty inexpensive. Pay attention to magnetic polarity instructions as some sensors are more sensitive to this than others.
 

Eagleboy

Novice Member
I did short the alarm wires out and the alarm system was then operational so everything pointed to the reed switch. New reed switch fitted and alarm now working. Thanks for your advice.
 

wilbanat

Distinguished Member
Having similar problems. My alarm system is about 9 years old and have a similar switch to the photo sent by the member. The alarm control panel is showing that the front door circuit is open when the door is closed. Will I need to shut the power off to change the switch? Thanks
Nope, no voltage at all to a door contact
 

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