I have a 1986 190D

I returned to my car after it being parked for a couple hours today and the horn was blasting at an even, steady interval.

I didn't realize it was my car at first, and when I put the key in the lock to open the door, it stopped immediately.

I am unable to recreate the alarm. I tried to set it off and can't get it to happen. I do see what looks like a horn and some additional wiring in front of my battery, so I think I found the unit. It appears to be factory.

I don't see anything in the interior of my car or anywhere else that would enable or disable a car alarm.

Did these cars come from the factory this way? If so, any idea how to turn it on and off?
Thanks.

On my SEC it's set automatically.

If I leave the hood down but unlatched after a "while" never timed it.

later I open the hood, the alarm goes off.

Same thing if I open the trunk (left unlocked) without the key.

If its anything like my old w124 Try this: Roll your drivers window down. Get out and lock the car. Now reach through the open window and unlock and open the door. The alarm should go off. It is automatically enabled\disabled via the key locking and unlocking the car.

Pretty sure thats how it worked. It's been a long time.

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

dude99. Interesting enough, I tried your procedure and it worked. But the horn only blasted once when I reached through the open window and opened the door from the door handle.
If I reach through the window and lift up the lock, and open the inside door handle, the alarm does nothing.

So, I got it to blast once but can't recreate the constant blasting of the horn when the alarm went off.

We’re the lights all flashing when it went off with the single horn blast? It’s probably just a dud module. I took the factory alarm out of mine, it was too much trouble.

On some models, if the battery is disconnected or the radio is removed with the alarm active, it will disable the radio and require a code to re-enable it. Is this one of those cars? I don't know, just trying to prevent a mishap in case it is.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
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I didn't notice the lights flashing when the alarm went off repeatedly. Michael, The radio is not original to the car. I don't think there are any codes to re-enable anything, It is an 86 190D, pretty simple. Thanks for the heads up though, I will check that out.

dude99, I will have a look at the module as wel...l It may be bad.