1989 560 Sel-alarm Problem
 

How to reset factory alarm.Sometimes comes on by its self.

Same problem with an '89 420 SEL. If I open the trunk after I park, the alarm comes on about ten minutes after I lock the car. If I lock the car froom the trunk, does the same thing. I replaced the driver's door handle a year ago thinking the switch in there was bad, $330, not available aftermarket, didn't help. Now, I just restart the car after the trunk is opened and make sure the car is locked from the door. To shut off the alarm, unlock the trunk with the key. Do you sometimes not get the rest of the doors unlocked from the inside when you pull the doorhandle? Mine's doing that, too, and I think it's related.

on my 91 560SEL, I decided to just disable the alarm from under the floor-front passenger seat well. It was also intermittent at best.

I have heard of many people doing that....I am thinking about doing the same and getting an aftermarket alarm, maybe one with one of those pagers. I also want keyless entry. BergWerks supposedly has a good keyless kit.

alarm
 

Hello,
I'm searching back in my memory quite a ways, so forgive me if I'm mistaken, but I believe the problem you are having with your alarm is a malfunctioning tow-off sensor. These were originally installed to set off the alarm if the car was lifted with a tow truck or a flat bed. It is white in color and should be located under the rear seat on the driver's side. Just unplug it. I was a factory tech from 87 to 94 and can tell you that this does not interfere with the operation of the alarm in any other way. Hope this helps.
Mike H.