Car Alarms: 98 Lexus ES300 Alarm/door lock issue, keyless entry system, remote keyless entry

Question
I have a 98 Lexus ES300 with factory alarm. For over a year, the alarm goes off on its own randomly, but mostly when the door is locked – especially overnight. The headlights flash and the car horn honks. Not sure what display is doing - when I unlock door with fob alarm turns off. After a few seconds door locks back by itself and alarm may go off again. But if I use inside door panel switch to unlock, it stays unlocked. So I leave car unlocked whenever possible. At work I park in gated lot and leave it unlocked during day, but security told me the alarm was going off during the day. So I had the horn disconnected, but alarm will still go off with flashing lights. Recently, when I lock car overnight, in the morning it won’t crank right away like battery drained, but when I keep trying after 5-15 minutes it would eventually start. Concerned about battery going dead, I had it tested & mechanic said battery needed to be replaced. I just replaced the battery and it still seems like battery dead in the mornings if I locked door previous night. Also, my key fob hasn’t been working well in recent weeks. Before I could lock/unlock doors from several yards away, now I have to be right at the doors and press a few times before it locks/unlocks. And occasionally, the locks will cycle to unlock the doors two or three times when the driver's door is opened and closed.What could be the issue(s)? Thanks!

Answer
This "factory alarm", like most all other Japanese
factory alarms, works with the physical action of
locking/arming and unlocking/disarming.
They are intertwind.

There is no single wire to ground or,
spice into. To disarm these, a remote keyless
entry system would be required.

Of course the key in the drivers door, turn left
first to engage the alarm, then right to unlock
and disarm it, is how a factory alarm can be disabled
as well if it's working. But if damaged in some way,
the only other way is to add a factory remote from the
dealer, or an after market keyless entry system to make
the lock mechanism control the factory alarm.

*note:
do a test for me. using your KEY ONLY,
take the battery out of your key fob.
Go for a week without it.

If no trigger of the system, then that's
not it. If it does trigger in that time period,
then look for damage in the doors somewhere near
the locking mechanism.

Wish I had an easy to do method for you, but
I am just the messenger. I only get around the
stuff they throw at you all here! lol.

I hope this was helpful.

ALARMTEK
CARALARMMAN.COM