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Alarm going off randomly
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Posted 10/14/2020 12:14 AM
koly
Elite Veteran




Date registered: Jul 2006
Location: Scottsdale, AZ USA
Vehicle(s): 2000 G500
Posts: 816
500
Alarm going off randomly

Not sure why, but the G’s alarm has gone off for no reason four/five times now. I know no one /nothing has set it off from video reviews, so I’m wondering what could be causing it. The first two times it happened within the same 24 hrs. Then no problems for a week or so. Then nothing for over a month until this evening.

Possibly related, I was having problems with the central locking working and replaced the kirkut (sp/from memory) relay, but that 6-8 months before this started. Also, my front passenger door lock actuator is bad and can’t unlock the door, but the system hasn’t had any issues with that before (it’s been bad for several years).

Thoughts?


#242093
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Posted 10/15/2020 3:37 PM
Floobydust
Veteran




Date registered: Mar 2014
Location: Massachusetts, USA
Vehicle(s): 1995 E320 Cabrio, 2003 G500, 2000 SL500, 1980 TR8
Posts: 279
100
RE: Alarm going off randomly

I'm not sure if this is true of a 2000, but the later G's have an alarm horn that has a built-in battery backup. When that battery starts to fail (or fails), the horns will sound randomly (usually a few minutes after the alarm is armed). I went through this on my '03 and had to replace the alarm horn.
#242095 - in reply to #242093
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Posted 10/15/2020 7:00 PM
koly
Elite Veteran




Date registered: Jul 2006
Location: Scottsdale, AZ USA
Vehicle(s): 2000 G500
Posts: 816
500
RE: Alarm going off randomly

Worth a look, I guess - where was your alarm battery backup?

I'd be shocked if the original battery has lasted almost 21 years....

My random alarm issue has never gone off a few minutes after locking - it's usually been at least several hours.
#242096 - in reply to #242095
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Posted 10/15/2020 8:17 PM
paulunm
Regular


Date registered: Jan 2015
Location: Los Angeles
Vehicle(s): 2000 G500
Posts: 96
50
Re: Alarm going off randomly

This is seemingly more common these days. If you have a bad lock actuator- I'd start there.

Try hitting the tow button just before you lock the truck- see if that keeps the alarm from going off. If it does, you will be interested in this-

As I say in the below thread, I suspect the tow sensor is bad. I tried ordering one, mboemparts says it's NLA, so now I'm checking with Classic Center.

https://clubgwagen.com/forum/viewtopic.php?f=18&t=17919

Edited by paulunm 10/15/2020 8:18 PM
#242097 - in reply to #242093
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Posted 10/16/2020 4:23 PM
koly
Elite Veteran




Date registered: Jul 2006
Location: Scottsdale, AZ USA
Vehicle(s): 2000 G500
Posts: 816
500
Re: Alarm going off randomly

paulunm - 10/15/2020 6:17 PM

This is seemingly more common these days. If you have a bad lock actuator- I'd start there.

Try hitting the tow button just before you lock the truck- see if that keeps the alarm from going off. If it does, you will be interested in this-

As I say in the below thread, I suspect the tow sensor is bad. I tried ordering one, mboemparts says it's NLA, so now I'm checking with Classic Center.

https://clubgwagen.com/forum/viewtopic.php?f=18&t=17919

I'll try that this weekend - of course, it'll be kind of a blind test, as my alarm's randomness is so long between going off on its own.

From your other thread, what if you just unplug the tow sensor rocker switch?
#242098 - in reply to #242097
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Posted 10/16/2020 5:33 PM
paulunm
Regular


Date registered: Jan 2015
Location: Los Angeles
Vehicle(s): 2000 G500
Posts: 96
50
Re: Alarm going off randomly

I don't think unplugging the tow switch (button) will keep the tow sensor off. I had a bad tow sensor that I recently replaced- the light wouldn't illuminate- when I replaced it I was able to then turn off the tow sensor.

Certainly worth a try as it's really easy to get to. But again with a bad lock actuator, I'd start there. Then try to unplug the tow sensor itself.

Also, Classic Center confirmed today that our tow sensor is NLA.

Edited by paulunm 10/16/2020 6:01 PM
#242099 - in reply to #242098
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Posted 10/17/2020 5:49 AM
Inkblotz
Expert




Date registered: Apr 2006
Location: Georgia
Vehicle(s): 90 300GD "Thundering Turtle II", w/ 603A turbo
Posts: 3118
2000
Re: Alarm going off randomly

I would be leaning toward the lock actuator as well. Different car though still Mercedes; my wife's 04 C260 wagon had the same thing happen. It turned out to be a bad lock actuator for the rear the hatch.
#242100 - in reply to #242093
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Posted 10/17/2020 11:03 AM
paulunm
Regular


Date registered: Jan 2015
Location: Los Angeles
Vehicle(s): 2000 G500
Posts: 96
50
Re: Alarm going off randomly

I'll also add that if you have the truck scanned with a STAR or similar scanner, it will tell you what last set off the alarm. Mine specifically said it was the tow sensor. Would also tell you that a door sensor set it off.

Come to think of it though- the door sensor is a totally different part than the actuator. You can unlock the passenger side door without setting off the alarm, only when you actually open the door does it set off the alarm.... But, can't hurt to change the actuator, and it's sorta fun. Also a good opportunity to reseal the vapor barrier with some caulk strips.

Sorry for thinking out loud here...
#242101 - in reply to #242100
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Posted 10/17/2020 3:26 PM
Rich
Regular




Date registered: May 2006
Location: Elkins Park, PA USA
Vehicle(s): 2005 G500; 1985 280GE cabrio
Posts: 62
50
RE: Alarm going off randomly

My 2005 did this a couple of years ago. The fix...."removed and replaced faulty alarm siren".
#242102 - in reply to #242093
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Posted 10/17/2020 7:13 PM
paulunm
Regular


Date registered: Jan 2015
Location: Los Angeles
Vehicle(s): 2000 G500
Posts: 96
50
Re: Alarm going off randomly

The pre 2002 don't seem to have the battery in the alarm horn.

I unplugged my tow sensor today, which required removal of the center console. Wasn't fun, but seemed to have stopped my alarm from sounding. That also maintains the intrusion alert, whereas if you unplug the alarm module entirely you lose that functionality.

Edited by paulunm 10/18/2020 9:47 AM
#242103 - in reply to #242102
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Posted 10/17/2020 10:12 PM
otiswesty
Expert




Date registered: Jun 2007
Location: Portland, Oregon
Vehicle(s): 460 461 463
Posts: 2780
2000
Re: Alarm going off randomly

My first thought would be to go ahead and replace all of the door sensors as well as the hood sensor. They go bad and if they are over 10 years old, it is a good preventative maintenance action regardless. Agree with the points others have made as well, but I have yet to experience any alarm issues on my 1999.
#242104 - in reply to #242093
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Posted 10/18/2020 2:10 PM
gbenzer
Extreme Veteran




Date registered: Dec 2006
Location: Georgia
Vehicle(s): 2007 G-500, 2017 Audi Q7
Posts: 412
300
RE: Alarm going off randomly

I had a random ABS light issue for 6+ years and replaced a bunch of items related to the ABS system. The problem was finally solved when I fixed a faulty connector. All the components of the system were ok but the intermittent conductivity of 1 simple connector is all it was. The cost to actually fix the connector was zero but I spent a couple of thousand dollars replacing things over the 6 years. The error code was "front left wheel speed sensor". I mention this especially if the alarm circuit operates on a closed loop system that alarms when the loop circuit is broken. Good luck.
#242108 - in reply to #242093
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Posted 10/18/2020 5:40 PM
koly
Elite Veteran




Date registered: Jul 2006
Location: Scottsdale, AZ USA
Vehicle(s): 2000 G500
Posts: 816
500
Re: Alarm going off randomly

Worth it to replace the door actuator, but since that one hasn't worked in ~5 years I don't think it would suddenly become the culprit.

#242110 - in reply to #242101
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