87 300D factory alarm wakes neighborhood - PeachParts Mercedes-Benz Forum

Full Monte · #1 12-28-2006, 09:43 PM

OK...I get tired of the 2:30am to 4:30am wakeup calls from the Benz alarm system. So are the neighbors. A pro mechanic told me to replace the hood switch. It seemed to help...for awhile. Now the alarm is back to its old tricks. I read another thread here about disconnecting the alarm box under the passenger footrest. Apparently, they moved it elsewhere on the 87.
I'm ready to disconnect it if I can't fix it. Any ideas would be appreciated.
My neighbors would appreciate it too!

speedy300Dturbo · #2 12-28-2006, 09:48 PM

The alarm control unit is underneath the front passenger's floormat, behind a black plastic "trap door". It's highly unlikely that someone relocated the control unit. Maybe the previous owner had an aftermarket alarm installed and removed the factory control unit?

Motorhead · #3 12-28-2006, 10:05 PM

Every car I have worked on that had the factory alarm was disconnected because they went haywire

Wait til the thing doesn't let you start your car somewhere and strand you. Been there...Done that....

greasybenz · #4 12-28-2006, 10:18 PM

yeah its disconnected on my 87. Just remove unplug the cable from the metal box under the passanger side floormat.

Full Monte · #5 12-29-2006, 01:02 AM

Quote:

Originally Posted by speedy300Dturbo

The alarm control unit is underneath the front passenger's floormat, behind a black plastic "trap door". It's highly unlikely that someone relocated the control unit. Maybe the previous owner had an aftermarket alarm installed and removed the factory control unit?

There's a black plastic box under the floor mat close to the door and just in front of the seat. I opened it up and there are some wires running through there, but most of it is empty space. Whazat mean?

Johnhef · #6 12-29-2006, 09:58 AM

My 87 had it disconnected when I bought it. I plugged it back in and have only had 2 middle of the night problems (very windy nights) in the last 3-4 years. I can live with that as long as does its job if someone tries to get in

Matt L · #7 12-29-2006, 11:09 AM

Note: don't break into John's car on a calm night.

Full Monte · #8 12-29-2006, 02:05 PM

There's also a plastic box under the angled foot rest on the passenger side, but no metal box. Could this be the alarm system?

Johnhef · #9 12-29-2006, 02:17 PM

one is for airbag and one is alarm, dont unplug the red connector! to test it, pop your hood with the alarm "armed"

Full Monte · #10 12-31-2006, 12:13 AM

This is getting serious. I was awakened at 3:55am by the Benz again.
I can only find one box under the passenger footrest and it's plastic, not metal. I looked at the manual from a friend and it talks about a Marten security system. Unfortunately, the diagrams don't point me to the correct location for the "brain" of the system. It points to a location up close to the radiator. I can't find it there. Does anyone have another idea? I would like to disconnect it. Thanks!

dieseldiehard · #11 12-31-2006, 01:13 AM

The horn for the alarm is all by itself, mounted near the brake booster. Just disconnect it and see if that isn't the quickest fix. But don't jump in and drive off with the headlights flashing, the police my stop you to see whats up! My blue 87 does that once in a while if I open the car from the trunk, I figure its a bad switch but I've no time to look for that problem. Stupid alarms were in the news back in the '80s when they made fun of Mercedes alarms whenever the humidity was high enough there were a number of them going off all over town. I guess lots of them got disconnected then. So much for fine German engineering!
Then there was the time an MB representative was delivering a car for some important event in the US where Mercedes was to debut this car with "Important New Safety Features!" I think it may have been a 124. Anyhow, as he passed a police car that happened to be transmitting the air bag went off! Needless to say that car didn't make it to the press release! They tried to keep that out of the news but its still alive thanks to the Internet (and the ShopForum)

speedy300Dturbo · #12 12-31-2006, 01:21 AM

Quote:

Originally Posted by Full Monte

There's also a plastic box under the angled foot rest on the passenger side, but no metal box. Could this be the alarm system?

The plastic box which says BECKER on it is the alarm control module. It looks like this:

Full Monte · #13 01-04-2007, 04:12 PM

OK...I think it's disconnected. At least it hasn't awakened the neighborhood for two nights in a row. What confused me about it were the discrepancies between what the manual was saying and what the guys on the forum were saying. I was looking originally for one metal box of two boxes under the passenger footrest, then for a module near the radiator. There was only one box under the footrest and it was a plastic one. I was afraid it was the airbag controller, so didn't disconnect it. Speedy's photo assured me that I was really looking at the security system controller, so it gave me the confidence that if I disconnected it, the airbag wouldn't go off. Thank you guys for the advice, and thank you, Speedy for the photo.

I hope this thread helps others navigate this problem on the 1987 300D. I think most people would rather have a non-working security system than one that forces you to leave the doors unlocked overnight.