There are two types of factory alarms, one that uses a
remote control and the other is activated when the car is locked with the key. It is
just a matter of convenience of having the keyless entry and being able to open the trunk
from far away.
Factory alarms are as good quality or better than
aftermarket alarms. They are very reliable and don't usually give false alarms
(unless the owner does not know how to use them, which is common). Most do lack
features such as microwave, shock, glass breakage sensors, etc. and are hard to customize
The main problem with factory alarms is predictability.
An experienced thief knows exactly what to do to disable the alarm before even
breaking in the car. All factory alarms are installed the same way and in the same
location for a certain model car. All they have to do is snip a single wire or
remove a fuse. It only takes an experienced thief a few seconds to disable a factory
Aftermarket alarms come in many different flavors, from
the cheap 2-wire voltage drop sensing alarm, to high-end custom alarms that range in the
$1,000s. They present more installation and configuration options, and can be
easily customized and upgraded.
The predictability factor is somewhat decreased because
installation depends on the installer. Different installers, even working for the
same company, do different things. I said somewhat decreased because most shops use
the all to common alarm wire-tied under the dash and starter disable tapped at the most
accessible spot under the steering wheel column installation. This actually makes it
easy for a thief because all they have to do is unplug the brain to disable the alarm.
If they want to steal the car, the starter wires are already "pointed
out" to them.
Even if a thief can't get to the brain to disable it
they can easily kill your alarm. Picture the following scenario: A thief
breaks the glass, pops the hood, opens he hood and cuts the siren wires or battery wires.
How long did the alarm made noise? Not very long, maybe a few seconds.
All the people that heard the alarm probably thought, there goes another one that doesn't
how to use their alarm.
If you want a good alarm system, the best thing to do
is first, tap into wires and mount the brain in inaccessible locations. The next
most important thing is to install a hood lock. If they can't open the hood, it
makes it a lot harder to disable the alarm. Add a battery backup to the alarm for
extra piece of mind.