Car Alarms: Car alarm going off every now and then, pin switch, knee level

Question
Have a 2001 Ford La Chateau van that sets in drive way for months at a time.

The car alarm (factory) horn will some times sound and I am told it is because car battery gets low and it thinks it has been entered by  a thief.

I disable it by turning key in ignition and pressing kill button at knee level.

We have started to run van just in the last few days and it went off today which surprised me.

Can you tell me what might be wrong as the battery is relatively  new and should be up.

Answer
I'd start with replacing the battery, not recharging it.
All "factory" alarms work on battery drain. If it detects
a 2% spike or, dip, it will report it.

If the battery is up to snuff, then you may have another
deeper, issue.
From what I can tell, this vehicle does not have Ford's PATS
(www.FORDPATS.com) in the ignition, so it's difficult to
tell what it is from my perspective other then a damaged
door lock or pin switch in the truck.

If it's simply a faulty security system, go to
www.WIRWERX.com and get the OEM disarming
data for terminating the horn honking headlight flashing
security for good. No more alarm, but if that does
not bother you, the 4.99 fix will be a bargain.

ALARMTEK