Alarm goes off for no reason- what's the fix.
 

86 560sl.

Sun. AM Car in driveway, unlocked. All of a sudden the alarm goes off for no apparent reason. Before I could get to it to turn it off, the alarm quits not to be heard again all day.

Mon. AM Walked around the car to get in and the alarm goes off again. I had not done anything, not even sure I had opened the car door. I put the key in the ignition, didn't kill the alarm. Started the car, alarm still sounding. I put the key in every lock on every door and rear deck and the alarm wouldn't go off. It seems to be on a 30 sec cycle where it would stop itself but within a few seconds would start up again.

I disconnected the battery and went to the bank in my truck. About an hour later I reconnected the batter and the alarm immediately went off. After it stopped, it hasn't gone off again.

Sheesh, I just now convincing my wife to take this car occassionally but this will pretty much kill that.

Any ideas on what broke or better yet how to take the alarm out of the loop altogether?

Thanks.

JB

this happens sometimes to me in the CE... i just lock it up and unlock again... it goes off after going through a cycle ...or so it seems.

This problem coincided with my door buzzer going off anytime I open the door... every once in a blue moon you can open the door and the buzzer doesn't go off...but I can't figure it out.

the alarm thing has only happened two or three times in the last year.

Mine is/was microswitch at tumbler of drivers door lock. Water eventually works in there and messes with the microswitch. I think you have switches in both front doors and trunk on the '86. Disconnect the alarm under the passenger footwell cover (black) for now. Assuming factory alarm.

One of my 87 sdl's had an errant alarm, so I just started using the round key with no red dot to lock & unlock the car.

In another post- I was referring to a beautiful, blue 86-91 LWB 126 sedan that was for sale at a local car lot.

One evening last week I drove by and glanced over and the alarm was going off and the lights were flashing. Wonder if this is the same problem on this car? Could have been where someone may have tipped off the alarm though.

I just thought it was most odd.


BTW - what was the first year for the factory alarm? Does my 85' have an alarm, or was this too early? How can it be tested?

1984. Lock it up with a window open and then open the door thru the window ;) Look under the false footwell, passenger side for a Becker box.

Thanks. That is what I was thinking I should do to test it- at least that is how we tested my grandfathers 90' Mazda.

I will try that to see if it works. Was it optional on the 84-85 models?

If I do have one and I set it off the way you suggested- how do I shut it off? Shut the door and unlock it with the key?

Thanks!

Don't know optional/standard. I think mine came with it off the dealer floor (not ordered), but that was a lifetime ago.

Key turns it off (if it works right).

86560SEL said: If I do have one and I set it off the way you suggested- how do I shut it off? Shut the door and unlock it with the key?

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Your alarm should shut off when you insert the ignition key in either front door and unlock the door.