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Can I Disable the Alarm??

22K views 29 replies 13 participants last post by  devilmaycare 
#1 ·
Does any one know if I can disable the car alarm. It would be nice to leave the sun roof open or a window partially open on these hot days without a bug flying in and setting of the alarm.
 
#2 ·
I don't think so, I have the same problem
 
#3 ·
From the look of the wiring diagram it should be possible to interpose a single pole switch between the sentry module and it's power feed - there is a Red/Yellow wire leading in to the sentry module that comes from the fuse panel (Fuse 14) so a switch in that circuit should allow you to disable the alarm.

Alternatively there would be a signal wire from the sunroof into the CAN bus that could similarly be interrupted with a switch. This naturally assumes that the sentry module doesn't check for input signals from the sensor.

Cheers
Russ
 
#4 ·
I have the same prob but have found that if i leave the sunroof open with the cover closed up to only a very small gap the sensors don't set the alarm off. Hence just looked out the window to the garage and the sunroof is still open from yesterday afternoon and yes the car is and has been locked the whole time.

Just what i do on hot days
 
#5 ·
Hi all

This approach may be a little low tech and I haven't tried it (no sunroof) but.....
as it's the ultrasonic sensor that's picking up any inside movement - flying bugs or anything else
it should be possible to mask the sensor (literally) to stop it "seeing" so to speak.
A small piece of electrical or masking tape over the sensor (situated about rear right passenger head level, c-pillar) should do the trick :)

This way the car security is still armed but the cabin is isolated (I hope).
Any feedback would be appreciated :biggrin:

Cheers
 
#8 ·
Just been down the shed and can confirm.......Jaffa was spot on, all I did was use a few pieces of electrical tape on the drivers side rear passenger sensor on the C-Pillar to test and it did work, the alarm did not activate while I was sitting in the cab trying yoga :biggrin: :biggrin:

Nice work mate :)
 
#10 ·
The 'sentry module' Russ was reffering to, is the wireless control module (wcm). This is for the immobiliser, tpm & rke systems.
The intrusion alarm is a seperate sytem, operated by the intrusion module (itm).
Cutting power to the wcm will cause all sorts of problems.

You can tape the sensor as described, unplug it, or unplug the itm which *should* still allow the alarm to operate if doors, hood or trunk are opened (*i haven't tested this though).

"The intrusion module has two integral mounts that are secured behind the passenger side instrument panel, just above the glove box."
 
#17 ·
Hi M@ndrake

There are actually 2 sensors. You refer to the front sensor. I suspect that is the transmitter and the rear is the receiver.
The Tx creates a ultrasonics field in the cabin. After the doors & sunroof are shut the field settles and the Rx sees a constant field level. The alarm design allows some seconds settling time before arming.

Ultransonics sprays everywhere and is easily affected by wind movement or change in space volume. e.g. air movement from open windows, broken window or when a door is opened. Any variation in the field is sensed as intruder alert. That's why it's more effective to tape the RX than the Tx.

Taping up the rear sensor is probably enough for this exercise but why not tape both to be sure :biggrin:

Cheers
 
#20 ·
Hi M@ndrake

That's a good question and requires some thought to do it justice.

We live in a world of sound (audio) and noise (electrical). Both are frequency related.

e.g. human voice is around 200Hz to 4.0KHz so the telephone networks evolved with 300Hz to 3.0KHz
A good stereo or 5.1 audio amplifier may be 20Hz to 20KHz
Human hearing (young) may hear up to 17KHz. Remember the high pitch whistle from the TV? 16.25KHz.

Typically adults have some hearing loss and only reach 12KHz. Can't hear the TV whistle anymore
Animal hearing (dogs) can hear up to 40KHz.

Ultrasonic frequencies typically 20KHz to 50KHz don't travel very far and are easily contained within walls of glass, wood, cement, brick, metal, plastic or anything solid. For low level signals even electrical tape :)

The Park Assist also works on ultrasonic frequencies. The reflected signal level at the receivers are converted to represent distance on the rear window LED's display.

Without going into practicalities of antenna systems, power amplifiers etc suffice to say: If you want to project a signal any distance then a higher frequency is required e.g.
AM radio 535KHz to 1700KHz (1.7MHz)
CB Radio 26MHz to 30MHz
VHF TV 54MHz to 88MHz
FM Radio 88MHz to 108MHz etc
These frequency signals can travel through walls etc and cannot be contained easily. Hence better radio & tv coverage.

Cheers
 
#22 ·
Sort of.
The ultrasonic transducer design for air transmission are inherrantly low power devices. Air is very lossy medium for acoustic (pressure) wave transmission.
Piezoelectric transducers don't move much compared to e.g. a loudspeaker. Gases (air) have loosely connected molecules so require large movement transducer otherwise the pressure wave is absorbed within short distance.

However ultrasonic transducers (40KHz to 300KHz) are used in water which is a much better medium to transmit acoustic pressure because the molecules are tightly packed together e.g.
medical ultrasound for checking baby development
marine depth sounders, fish finders, sonar location etc

Cheers
 
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