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Discussion Starter #1 (Edited)
Alarm goes off for no reason - TSB issued by smart

My smart is parked and locked and nobody is doing anything yet in the middle of the night the alarm has gone off... 5 times now. It has happened three nights thus far.

There is no shock sensor on the alarm so as far as I know the alarm will only go off if there is an unauthorized opening.

Has anyone else had this happen? Car is three weeks old tomorrow.
 

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This has been an issue with a few smarts with factory alarms. Seems to happen more on cabriolets. As far as I know a suitable solution has not been discovered. Most people push the tow button on the button bank for the alarm and then lock the car. This should prevent the alarm from going off in the middle of the night.
 

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Double check that the service hood is shut securely, and locked. Also double check that both the hatch and glass upper are shut tight. These 3 things can sometimes not close all the way, which may cause the sensors to activate the alarm.

I've had my alarm go off once unexpectedly when I was fiddling with the service hood. As well I've had my hatch not shut properly (appeared shut) but it was ajar enough to not allow me to lock and arm the system.
 

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The alarm was quite often going off at random in my 451. Have yet to even hear it, let alone voluntarily find out what the alarm sounds like, on my 453.
 

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I don't know if this applies at all to a 453, but, FWIW, a number of the 2008 451's, mine included, had a similar problem. In nearly all of the cases it was caused by a faulty interior motion sensor. (That's why pushing the button temporarily "cured" it. The button turns off that sensor.) In my, and most cases, replacing the sensor fixed the problem.
 

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Discussion Starter #7
So the alarm likes to go off at 12:15AM, 12:30AM, or 1AM. Last night it went off at each of those times. I checked the "hood," doors, and rear hatch before I left the car yesterday and it was all secure.

Each time the alarm went off (and woke me up) nobody was anywhere near the car.

I don't think this car has a shock sensor because I tried rocking it back and forth and nothing happened.

I also parked the car 3 hours earlier than usual so it can't be because it has sat inactive for X amount of time.

Perhaps there is something that "wakes up" at those times?
 

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I had this happen on my 09 Cabrio. It turned out to be a slightly mal-adjusted microswitch on the right side of the tailgate. A tech at the smart center BENT the actuator arm to fix it. When I arrived home 3.5 hours later, the car doors would not lock and stay locked. Just like if you try to lock the doors with the tail gate open. NOT good. The next day I took off the rear tail gate shell to access the BENT actuator and re-formed it to a more natural condition within specs. and have not had a false alarm since. It used to be sensitive to wind gusts when parked and alarm armed, but that was just the microswitch being adjusted on the ragged edge of specs. So check the switch first. It doesn't cost a thing to check out that adjustment yourself.
 

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Discussion Starter #9
I read your post about that... must be what it is I will concentrate on making sure the tailgate is fully locked. It is just off that every time it has gone off it has been around or after midnight.
 

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Discussion Starter #10
I'm bringing it in for service on Tuesday.

Looks like 4 hours after I turn off the motor the alarm goes off.

I parked it at 8 the alarm goes off at 12. Parked it at 12 alarm goes off at 4. Tonight I'm going to park it at 10 and see if it goes off at 2.

Needless to say, my neighbors are unhappy and I'm not getting a good night's sleep.

Based on this it couldn't be a micro switch. There has to be something in the smart's brain that switches on 4 hours after it's parked to check something and this is tripping the alarm.
 

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I don't know if this applies at all to a 453, but, FWIW, a number of the 2008 451's, mine included, had a similar problem. In nearly all of the cases it was caused by a faulty interior motion sensor.
My 451 also had this issue, because the sensor was initially "put in upside down".

The motion sensor is also notorious for going off if/when frost forms on the sensor. Because of its location, it's rather susceptible to attracting moisture from the near by carpet or from the channel of air that flows past it. If that moisture settles on the sensor and then crystallizes, as those form, the sensor "detects motion" and goes off. Unfortuantely it's a royal PITA to wipe the sensor off and/or keep the car from collecting tons of water in the winter when there's snow.

This still happens occasionally with my 451, since snowy boots track moisture in. Usually it's several hours after parking, since the interior takes that long to hit freezing. The only real solution is to hit the button every time when it's going to go above/below freezing.

When I purchased by ED, I explicitly did NOT get the car alarm package as to explicitly not have to deal with this issue in the new car.
 

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Discussion Starter #12
I do not know if this car has a motion sensor. There is no button to disable for towing and I've tried violently rocking the car back and forth when it's been off and locked and it never made a peep.
 

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Based on this it couldn't be a micro switch. There has to be something in the smart's brain that switches on 4 hours after it's parked to check something and this is tripping the alarm.

My thought is far-fetched... but the coincidence is too strong not to mention:

The "from Start" statistical auto-reset (h, mi, mph, mpg) in the main dash pod will reset to –0.00– at precisely a 4-hour interval, if the car has not been restarted.

Could there be some interconnectivity?

(Edit: I really like that the OP is simply looking for a solution, and is not a whiner. (See gas threads if you don't get my point.)
 

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Discussion Starter #14
I appreciate your idea... I will have to discuss this with the service advisor.

Last night I drove the car and parked it and 4 hours later it went wacko.

Tonight I just started it but did not drive it. I will see if that makes any difference. Either the alarm will go off at midnight or 2am. Then I will know if driving it makes any difference. I cannot verify if it goes off when I'm at work as my car is too far away from me.

And you are right! Page 112 of the owner's manual:



“Complaining does not work as a strategy. We all have finite time and energy. Any time we spend whining is unlikely to help us achieve our goals. And it won't make us happier.” ― Randy Pausch, The Last Lecture
 

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Discussion Starter #15
I may have solved this. I thought about all the possible locations for sensors to get tripped and decided the ones for the "hood" would be most likely because it's the least sturdy area.

I removed my hood and put it back on and locked it (something I had never done). Oddly, 30 and 35 minutes later the alarm did go off for no reason I could detect but - most importantly - 4 hours later it did not go off and I slept through the night.

I think stevenvillatoro is right... 4 hours after being parked the car "wakes up" and resets itself and runs a quick system check and maybe then it detected something with one of the hood sensors. I hoped that by locking the hood it exerted a little more force towards keeping it shut.
 

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Discussion Starter #16
So nothing is working. I drove the car and parked it and it still went off at 12:15 AM even though it had been less than 4 hours parked.

Per the manual, pulling Fuse 7 deactivates the alarm... and the horn, sadly. So until I can get it fixed I'll have to pull the fuse each night when I park and put it back in before driving to work.

It's very tough getting the fuse cover in the glovebox open.
 

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Discussion Starter #18 (Edited)
I like your optimism. At this point, I wish I could share it.

I removed the fuse... not only is the cover extremely tough to get off but you have to have the hands of a 5 year old to reach it. Now the alarm can go off but there is no horn beeping... of course there is no horn at all as it's been disabled.
 

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If you can find the pins/sensors, maybe you can tape them down. Possibly the plastic panel is expanding/shrinking just enough from thermal change to set them off?
 
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