Alarm Sensors - What Type Are They?

[Shuggie]

Hi Folks,

Had a wierd one yesterday. The wifes hatch 2.2 d4d 06 alarm sounded twice in the driveway - all by itself. There was no major winds (or neighbour) that could have "rocked" the car. However, there was a gentle downward breeze that was blowing the plume of steam from our combi boiler vent dircetly onto/over the car.

Could it be that the alarm sensors picked this hotter air up via infra-red or some minor expansion contraction ? Don't know really... just wondering what type of sensors the default car alarm has and how it could be triggered. This is the only time its ever done this, so trying to rationalise why it did.

Any suggestions?

thanks

Shaun

[Heidfirst]

Could it be that the alarm sensors picked this hotter air up via infra-red or some minor expansion contraction ? Don't know really... just wondering what type of sensors the default car alarm has and how it could be triggered.

doubt it - I would imagine that it has voltage drop for the doors etc. & ultrasonic for the interior.

it's possible that with the cold weather that we've been having that the Battery voltage has dropped (especially if it isn't being driven much) triggering the voltage detection.