Editing Z31/Alarmsystem php (section)

=== Troubleshooting the Factory Alarm System ===

The Factory Alarm has several switches through the car. One on each door, One on the Hatch latch and one under the hood.

To work the circuit must be grounded to sound the alarm when an entery way is opened. This is One of the common points of failure, the "Door Closed" switch. In it's location it is exposed to water and Winter salt which can corrode the contacts preventing it from alarming when the door is opened. This one in particular has a hole worn through the rubber boot exposing the switch to the elements. As you can see the switch plunger has poked through the hole.


https://dev.z31library.com/xenonzcar_archive/z31/images/Alarm%20system/doorsensor.gif



https://dev.z31library.com/xenonzcar_archive/z31/images/Alarm%20system/doorsw1.gif


This is the door switch. In it there are actually two separate sets of switch contacts. One for the dome light and one for the anti-theft system. The one furthest back from the plunger with the red wire is for the alarm. The other contact with the black wire and red stripe if for the dome light. Both share a common black ground wire. The type of switch contacts are called "Self scrubbing". This means that the contact surfaces scrape or "scrub" themselves clean each time they close preventing corrosion buildup. This also means they do gradually wear out. A well designed switch is a balancing act between excess wear and corrosion failure. However, with a hole in the boot, as in the above image, corrosion can build rapidly causing the dome light or the alarm to not activate.