on later models you de-activate the alarm from the passenger side or the trunk lock. Have you tried this??

Disconnect that sucker or it will drive you nuts. Do a search on my name for a thread on this subject. Basically, you disconnect the brain box under the passenger footrest. If there is only one black box, it's likely to be it. If you see two boxes, be careful because one is for the airbag.

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1987 300D with 201k miles.
1985 F350 Ford dually 6.9 diesel
1988 F250 Ford utiilty truck 7.3 diesel

I read several threads on this subject, but need some clarification. Do I need to unplug both wiring harnesses going to the alarm brain?

Attached Thumbnails

 

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Both is good.

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Gone to the dark side

- Jeff

Thanks, Jeff.

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

I finally had to unplug mine after several months of intermittantly disarming when it should have and NOT disarming when it should have. Got tired of being embarassed by it in the school parking lot and went in there and disconnected the whole mess. Haven't looked back to it yet.

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Mine has been going off in the rain. Not that it rains much here. The ferries also set it off. I'm going to go and unplug it when the basketball game is over.

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Some pictures of the 124 alarm brain for future searchers.

Attached Thumbnails

   

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

How ironic......
I just got my other SDL back on the road about a week ago, and up until Saturday, did not think once about the alarm......BUT, Saturday, I unlocked the passenger door QUICKLY, and the second I opened it, the alarm went off.....what a surprise. Fortunately, it seems to work fine if you unlock and allow the locks to unlock all the doors first.

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87 300SDL - 215K Miles !!
99 F-350CC Dually PSD - 190K
86 300SDL - 189K
All on B-100

Just to set the record straight on unplugging the alarm system on a w126 1987 300SDL. You remove the black footwell panel after removing the carpets on passenger side that has labels containing the air bag system. It has a small plastic nut at the lower center that you remove with a 10mm wrench. Remove the panel and you will see 2 airbag modules, one in center and one on right. The alarm control box is to the far left and it is a black box that says Becker on it and has a black plug in on the left side of the box. Remove the plug and your alarm will be no more.

For safety sake first remove the negative ground battery cable and have the key switch to the 0 position before you work just in case you were to accidently unplug the silver air bag control boxes.

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Western NC
1987 300SDL W126 Turbo Diesel 335,000 + miles
1976 300D W115 275,000 miles+

Probear that is how mine works too. Yesterday my daughter opened the passenger door before all the locks had unlocked and beep, beep. She was in a hurry because it was raining.

Nothing I did would keep the alarm from going off. I have owned this car for 100k now and have never had any alarm issues. Today it started randomly going off at the opening of a door, trunk, hood, etc. I used the red dot key, opened slowly, disconnected the battery, held the key for 5 or more seconds each way....nothing would stop the alarm. So I found this post and disconnected the alarm once and for all. I am hoping that a 1987 300SDL is not on a thieves to do list anymore.....

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Western NC
1987 300SDL W126 Turbo Diesel 335,000 + miles
1976 300D W115 275,000 miles+

Don't just disconnect the alarm brain box, pull it out, and pull out the extra horn, and the tilt switch under the rear seat... it all adds up to about 5 lbs you're hauling around for no reason.

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Cheers!
Scott McPhee

1987 300D