Your car’s alarm system probably won’t age gracefully
Among the most common faults as cars age comes from those who don’t own the vehicle in question: the alarm system. Ask anyone what their favourite sound is in the middle of the night and car alarms will never be mentioned. Of course, this leads to the drivers hearing their least favourite noise: Neighbours sounding off on their doorsteps.
Alarm systems come in all types and with many different features, but they all have one thing in common: With age and distance travelled, they can be prone to failure. There are two main offerings: Factory and aftermarket-installed. So when dealing with glitches, knowing which system you have is important.
As with any system that involves electronics and moving parts, most troubles start with the moving parts. In alarm systems, those are the door, hood and trunk-lid or liftgate switches that let the alarm system know when something is open. Often these switches are incorporated into the door-latch assemblies and hard to access for testing without removing a door-trim panel.
Fortunately on factory (and some aftermarket) systems, these switches also control interior lighting. If your ride is sounding off with no evidence of actual tampering, one of the first DIY tests you can do is opening and closing each door with normal effort, while observing the interior lights to see if they turn off as intended. While sitting inside, push against each closed door to see if any dome lamp flickers; this would indicate poor contact action.
This method may at least let you know if one specific door is causing the problem, which can save a lot of time and money when you consult your mechanic for a resolution. With most factory systems, an onboard computer can retain some memory of door openings and closings, among other conditions, and a scan may help to confirm which door is the culprit. Few aftermarket kits have this level of self-diagnosis.
Another common cause of an alarm fault is a defective key fob. These handy little devices are abused on a regular basis, such as being run through a washing machine, dropped in water, or partially crushed under a foot.
If you want to eliminate a rough-looking fob as a cause, put it in a radio transmission-proof container for a day or so — it can be as easy as wrapping the fob in tinfoil and keeping it in your home freezer — to see if any problems suddenly disappear.
Sometimes, factory alarm systems can have their response mechanisms deleted or modified via a scanner tool and if you can’t afford the repair, at least you might be able to shut off the horn and flashing exterior lights.