So I take Greta out for a short ride today, her second since getting her street legal...I stop in my local Wawa (like 7-11 to the rest of the country) for a coffee, and lock the doors. When I come back out, I start her up, and the horn begins blaring, and the lights flashing! I am scrambling trying to figure out how to shut it off, it's sound accentuating "dumb guy, dumb guy, dumb guy" in my head. I got out and turning the lock again de-activated it.

So, not seeing something under the hood that looks aftermarket, am I to assume my 87 300D Turbo has a factory alarm? And if so, anyone have the sequence for turning it on/off? I am still waiting on delivery of all my manuals, so I would appreciate any info to keep me from looking like a total fool the next time I stop for java...I know this is punishment for laughing at everyone else with no grasp on their alarm all these years...



Mark

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Der Dieselschnell
1987 300D Turbo "Greta" 170k
1990 Ford F250 "Marnie" 93k

i feel ya, my car has an aftermarket audiovox system in it. big ugly black box on the wheel well and all. i figured since i didnt have the key fob, i would just unhook the 9 pin connector. WRONG. doing so turns off all buzzers in the car as well. so im just living with it for now. hoping that it doesnt decide to go off sometime like yours.

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1980 300D

You won't find any alarm info in the shop manuals. EVERY older Mercedes that I have known had alarm either disconnected or had problems like you have. It is really amazing that a car of such quality would have such a crappy alarm system!

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

that is funny. Just reminded me of when I bought my SD. I actually bought it not far from you in Walnutport. I used to live near Shawnee resort. I drove the entire way home from Quakertown to East Stroudsburg with my alarm going off and my lights flashing. I ended up cutting a few wires.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Most MB models of that era have an alarm system. You should have two keys, one has a red dot and one does not. The red dot key activates and deactivates the alarm when you lock and unlock the doors. If you lock it with the red dot key and then use the key without the dot to unlock the car the alarm will go off. But you can lock it by using the non red dot key and then the alarm is not armed.

Everything that Brandlj says is correct/accurate for your model.

The '87 300D alarm is standard, they all have 'em. Lock the doors or trunk with the red-dot key and it's armed. Unlock with same and it is unarmed.

People have problems with these alarms, the quality problem is with the diagnosis, not the alarm. It will alarm with door opening, hood opening, radio removal, car moved off-level (jacked up or towed), and with brake pedal depression. If it goes off unexpectedly it is most likely the brake-light switch or the metal tab that is supposed to be touching the radio casing metal.

The alarm system operation is in the glovebox/owner's manual, the shop manual has all of the schematics and service information.

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Gone to the dark side

- Jeff

The alarm on the SDL continues to work, knock on wood I havn't had this issue yet.

On the W126 the black box for the alarm is behind the passangers side foot well. Yank the carpet up, unbolt the plastic panal and its right there. Most people unplug them but they are usefull, its not a bad alarm system. Mine saved the SDL once so I wouldn't just yank the wires.

The red dot keys are obsolete and not needed.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

So can't you just scrape off the red dot to disable the whole thing ??

The red dot has nothing to do with the alarm. I think it was a marketing thing by MB to let everyone know they had an alarm standard.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The significance of the red dot is to let you know that this key is the one that arms the system. How does it arm the system? Simple. Look at the red dot key and the key without the dot and you willnotice that the red dot key is cut just a little bit differently. The extra cut engages the alarm sensor in the door lock in the door.
People with older cars that have continually used the red dot key for all of its life start to have problems with the alarm going off when they unlock their doors with the red dot key because the key itself begins to wear down and the little extra cut sometimes does not dis-arm the alarm when unlocking the door.
If you have this problem, find your other red dot key that has not been used every day and it will work like a charm.
The red dot is just a red dot, a little blob of plastic. No transponder or anything in it.
John
85 380se
86 300sdl
MBCA member
BMW CCA member

You may also just want to check for a toggle switch somewhere up in the driver side foot well - around where the fuses would be in most cars. That's what my car has, I assume it's aftermarket. If you have a toggle, you turn the key to number 2, then toggle back and forth 3 times. That turns mine off, but I'm sure it varies by brand.

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1983 MB 300SD Turbo Diesel

Ok I see now, just read the good old FSM. The red dot key just was another way of marking the master keys. Ie they open all the locks and shut the alarm off. MB got rid of them awhile ago, now they are just master keys. Cool stuff, I didn't know the guage cluster and brake pedal were also part of the system.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Is there an extra horn associated with the alarm systems? I had to replace the front right brake hard line on my 300D (W123) and I found a mysteriously buried horn bolted to the bottom of the battery tray. I thought I already had horns up front behind the bumper.

I also found a broken off pushbutton sensor located at the center of the firewall which appeared to have been pushed by the hood closing. Is this part of the alarm? My option plate codes (above the radiator) say I have an alarm system.

I had a replacement key sent to me from MB about 1year ago and came without the dot. Is there a way to tell whether the key has the alarm notch by looking at the metal? I think it is the master, since it unlocks the trunk and glove box.

Thanks for the info!

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Dave

2002 Audi S6 Avant
1983 300D
1984 300D (sold)
1990 560SEL (sold)

Had the problem with my 86 W201 which has the factory alarm system.
Ended up buying a new door lock into which you insert the key - not the mechanical lock. The unit is very expensive. If you have the factory alarm
you have in front of the fusebox another rectangular box. When remove the cover you will find 2 red fuses there. If you remove those alarm not working anymore. Agree, crappy sytem.

I don't know which car you refer to about the extra horn, but the '87 300D uses a separate horn for the alarm, its on the LF fender near the ABS pump. I disconnected mine.
My wife forgot and did something and found the headlights flashing on and off and in a state of panic tried locking and unlocking the car and it stopped. Its a crappy alarm but serves a purpose I guess. At least it doesn't have a motion detector that sets off when the wind blows or another car passing by rocks the vehicle and sets off a siren or bleeper or whatever some of the aftermarket crapola alarms have in them.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!