Alarm keeps going off

[Tehnation]

So I was parked in the street several days ago, and a massive storm flooded the street, not like hurricane floods, just a lot of water high enough to get my passenger side floor wet. Now when I arm the alarm it just goes off seconds later, something keeps triggering it. What alarm sensors are in the front or passenger side that would trigger my alarm constantly? I am thinking something is just wet and needs to be dried or blow some air on it. I was thinking its that box thingy next to where the 2 horns are located, it may just be the chirp thing when you hit the keyfob buttons. 

The trend for the past several years around my County is for these kids to go around neighborhoods in the middle of the night checking for open car doors and stealing stuff.... some people leave their keys in the car and have had them stolen. My Ring app everyday has videos of people just wandering driveways and private property looking for stuff in cars. 

[Tehnation]

anyone know how these car alarms work? 

I can't find any sensor in the fenders, but I found something about a shock sensor, thats supposedly under the passenger seat or something. 

 

Not sure if this is going in the right direction, any other sensors like this on the car? 

If my car wasn't so low to the ground I probably wouldn't have had this issue.... sigh.... I can't even get a normal jack under my car, I have to use a low profile jack. 

[Tehnation]

hmm wrong link

this is the link I was talking about.  I disconnected the sensor under the passenger seat and same thing. Not sure if thats cause it disconnected or not but not sure. 

 

[Tehnation]

Anyone know where this is located

https://parts.subaru.com/p/Subaru_2005_Legacy-25L-TURBO-5MT-4WD-GT-Limited-Sedan/Anti-Theft-Alarm-Control-Unit/49301042/88281AG10A.html

Or this 

https://parts.subaru.com/p/Subaru_2005_Legacy-25L-TURBO-5MT-4WD-GT-Limited-Sedan/Key-LESS-Control-Unit-Keyless-Entry-UNISIA/49300828/88035AG03A.html

[Max Capacity]

https://www.google.com/search?q=where+is+the+car+alarm+located+ina+2005+subaru+legacy&rlz=1C1OKWM_enUS906US906&oq=where+is+the+car+alarm+located+ina+2005+subaru+legacy+&aqs=chrome..69i57j33i10i160l3j33i10i299l2.28878j0j15&sourceid=chrome&ie=UTF-8

 

Maybe that will help ...

 

Go down a few post here, it's under the wiper arm... well that's the speaker location,

http://www.uklegacy.com/forums/index.php?/topic/133114-alarm-siren-going-off-by-itself-uk-spec-2005-legacy-wagon/

 

Found this in one of those post, 

It's just for making a noise. The Alarm ECU is behind the glovebox.

[Tehnation]

The alarm only goes off when I arm it, its like something is triggering it as soon as I arm it, then when hit the disarm button it stops while keeping the doors locked but the alarm is disarmed. 

I don't think its the horn or anything, all the horns are in the front passenger bumper under the headlight. Those videos seem to be for older models. 

Some sensor is probably wet, and keeps triggering the alarm as soon as its armed. So i am thinking it has to be some kind of sensor thats about a foot off the ground and on the passenger side. 

[Max Capacity]

Maybe reach out to Benny at https://www.subaruonlineparts.com/

 

You can PM him from the Vendor sticky above. Go to the last page and look back a few post. You'll find him. Maybe he'll tell you where to look.

[Tehnation]

Fixed it! 

I contacted M Sprank, and he said take a look at the ecu to see if it got wet, cause it spiders into all biu. But that wasn't the case, was nice and dry, I blew air on all the connections just to be sure. Got me thinking then I remembered I had disconnected the shock sensor. So I am assuming if you disconnect the shock sensor you will have the same issue I was having. If anyone wants to test this theory out, it would a easy way to troubleshoot the shock sensor.  Just unplug it and arm your alarm, if it goes off in like 30 seconds then we know that if that's disconnected or not working right, it will go off within 30 seconds.  I took it out, pulled out the circuit board, and there was signs of exposure to moisture, ie that green crap from corrosion, I sprayed it down with some electronics cleaner and scrubbed it with a toothbrush, got it as clean as i could get it, then actually turned down the potentiometer a bit, and now everything works the way it should! 

Those other two alarm things I linked are tucked up under the dash and way to high for any water to get to them , so those were rolled out when M Sprank told me where they were located, which pointed to only 2 things, the ECU and Shock Sensor, which are both floor level.

Another thing to note was when I armed it, the security light would just constantly flash. When it works properly its supposed to flash 2 or 3 times, then go off for a several seconds then flashes again 2 or 3 times, and repeats that process until disarmed. So if you see it constantly flashing when you arm it, you may have a problem with your alarm system shock sensor. 

[Max Capacity]

Glad you got it fixed.

[m sprank]

While I failed to recall the shock sensor under the passenger seat ( don't recall ever having an issue with one)  I am glad that pointing to the ecu and wire harness connectors led you to the eventual root cause.  Always happy to assist another member.   Unfortunately time away from the cars has diminished my (previously) encyclopedic knowledge of the cars.  The older you get, the more you forget.

[Infosecdad]

"The older you get, the more you forget." - m sprank

No kidding,  you just jogged the memory of me doing this exact thing a couple years ago when I swapped in STi seats and forgot to plug in the sensor under the passenger seat. Was so frustrated that the alarm would go off every time shortly after locking it.

[m sprank]

I used to joke that I had forgotton more about Subies than most owners ever knew about their cars. Seems like its becoming a reality. Lol.  Hard to believe its been over 21 years since taking delivery of my first WRX and starting down the rabbit hole. 

Edited September 21, 2022 by m sprank