The magnetic contact on my front door has stopped working. The rest of the system is fine. I've been quoted �45, plus parts - �7 'ish to fix.
Is this a simple job I can do myself, ie. replace the one on the door (2 screws) - no problem, but is there any wiring into the other one that requires a 'professional'?
The magnetic door switch has probably got a tamper circuit wired into it. You may have to program the control panel into Engineer mode to enable you to change the switch without triggering the alarm. A service engineer would usually take under a half hour to complete the task.
If it's a relatively simple alarm system (mine for example has front & back door sensors and 2 x PIR sensors) you can easily replace this yourself.
My front door sensor went a while back - �5 for an identical replacement from Maplin. As has been said just make a note of the wires. You shouldn't even have to change the magnet part attached to the door itself.
The other part is probably basically a reed switch and they do fail over time.