Alarm Keeps Activating

[Grahamr]

I have a 2001 Lexus RX300 and every time I leave the car and lock it, within three minutes the car alarm is sounding. I have changed the Battery, I have also checked and cleaned all door locks to ensure they are clean, but it is still happening. Can anyone make any suggestions?

[Herbie]

Does this happen wherever the car is parked or only in one place - just thinking radio interference?

[Delphius1]

If the car has the ultrasonic pack by the dome lights, then try and hold the off button on the ultrasonic unit for a few seconds to switch the sensors off an see if that makes a difference. The security light on the dash should flash rapidly when you press and hold the off button and that shows the ultrasonics are switched off.

That rules out sensor issues, or possibly a window slightly open messing about with the ultrasonic alarm sensors. I doubt in this weather you're leaving the sunroof open. ;-)

If the doors are left open, or the switches are broken to make the alarm think they're open the beeps sound immediately when you press the lock button, not after a few minutes. If the windows or sunroof are open a small crack, a breath of wind through the gap can trigger the ultrasonics and that can happen any time after the alarm is set.

Other than that, possibly a weak Battery draining too much too quickly may set it off.

Of course once storm Gareth has gone, if the alarm stops, then it was just the wind pushing the car around and triggering the vibration sensor.

 

 

[BachelorDays]

I remember reading in the manual for my RX 350 that the alarm system has a backup Battery of its own. The alarm will go off if this Battery is weak.