Help with my house alarm?

[KN4995]

Anyone have the slightest about door contacts on a standard house alarm?
I'm not completely in the dark with this particular alarm and how alarms work per se, but if I ever knew about contacts, then I've forgotten!

Last night, the alarm wouldn't set unless I omitted the back door.
Now, this has one of these reed(?) contacts as the pic below which I *think* are kinda like a magnet assembly?
One bit in the door jamb, the non-wired bit in the door itself.
Does anyone know what 'bit' usually breaks down in these?
If it's the wired end, do I have to wire right back to the box or is there a screw/terminal on the back of them? All the wiring is concealed you see.
Do they come as a pair or are they interchangeable - as in, do I just buy the one part or are they matched?
Where would I get something like this - Is it a standard B and Q job or specialist shop?
Lastly, is it likely that it is this that is causing the problem? I'm guessing as it's the only real part that comes under any usage (and the rest of the zones are fine) then it's going to be?

Thanks loads for any help.

[bopdude]

Your more likely to find it's a bad connection, rust build up on the connections on the door jam switch, a few ways to prove it, can you enter test mode ? if so, do so, then take off the magnet in the door and see if it activates when you hold the mag on the switch, if that doesn't work, try the contacts, (short them out ) you'll have to take off the switch obviously, should be slack somewhere to allow this, have you got a multi-meter ? if steps 1 and 2 don't work, your gonna have to bell them back to the box to make sure the wires ok, you will probably not need to go to this length.

HTH. let us know

[KN4995]

I have the bit out of the door and have held it to the contact on the jamb, but there's no difference. I was sure there would be to begin with, as I did manage to get it to settle today by pushing the door further closed - it's moved slightly with the mad weather up here, which I initially thought was the problem.
But now, I can't get it to settle, which made me think one of the bits may be 'gone'.

I'll prise the connection out of the jamb tomorrow though and inspect the connections - presumably it's a terminal - and short the terminal and see how I go from there.
Thanks for that.

I do have a multi-meter, yes - and the box is the closest to the switch so if a re-wire is in order it shouldn't be too much of a problem.

[bopdude]

Originally Posted by KN4995

I have the bit out of the door and have held it to the contact on the jamb, but there's no difference. I was sure there would be to begin with, as I did manage to get it to settle today by pushing the door further closed - it's moved slightly with the mad weather up here, which I initially thought was the problem.
But now, I can't get it to settle, which made me think one of the bits may be 'gone'.

I'll prise the connection out of the jamb tomorrow though and inspect the connections - presumably it's a terminal - and short the terminal and see how I go from there.
Thanks for that.

I do have a multi-meter, yes - and the box is the closest to the switch so if a re-wire is in order it shouldn't be too much of a problem.

If it has latched once today by messing around it doesn't sound to serious, I'm sure you'll suss it tomorrow when you get the other side out of the door all you have on the door switch are a couple of screw connections, nothing tricky about them at all, if it is giving you a hard time then maybe swap it out whilst you have it all stripped, only a couple of £'s per set, available in a lot of places

[KN4995]

Originally Posted by bopdude

If it has latched once today by messing around it doesn't sound to serious, I'm sure you'll suss it tomorrow when you get the other side out of the door all you have on the door switch are a couple of screw connections, nothing tricky about them at all, if it is giving you a hard time then maybe swap it out whilst you have it all stripped, only a couple of £'s per set, available in a lot of places

Brilliant.
Ta fella - I'll let you know how it goes.

[bopdude]

Originally Posted by KN4995

Brilliant.
Ta fella - I'll let you know how it goes.

Good luck