1988 W124 Factory Alarm Activation
 

How is the W124 Factory Alarm (1988 300TE) activated/on ?

My research has shown that I need to present the "black-box" with a "Ground" on a particular wire.

If I have to present a "ground", is it a continuous ground, or just a ground "pulse"?

Thanks,
:-) neil
1988 360TE AMG
1993 500E

The control unit is activated if there is a ground signal from any of the 4 doors (door jamb switches), trunk (trunk lamp switch), hood (seperate switch for anti-theft alarm), and possibly it may be activated by the ignition switch if the alarm is activate, and possibly by the brake pedal switch. There may also be a way the alarm knows the radio has been removed. No glass breakage sensor or anti-tow sensor on one that old, at least on the US versions.

Gilly

Neil, are you asking about what signal sets the alarm unit to be on the lookout for a break-in or what signal triggers the horns?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

What signal sets the alarm unit to be on the lookout for a break-in?

:-) neil

A signal from the drivers door lock cylinder. I think it's just a momentary pulse.

Gilly

Neil, I believe it's an impulse because the switch mechanism centers before you can pull out the key. Also, I have a bad driver side alarm switch and I use the same key motion to set and unset the alarm - I unlock the driver's door, open the door, twist the key to lock quickly so the alarm doesn't blare. Also confirmed by the W126 wiring diagram.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

If a pulse to ground to "arm" the alarm, then:

1) how long a pulse?
2) how do I unarm it/turn it off ?

:-) neil
1988 360TE AMG
1993 500E

I checked the W124 CD manual and couldn't find the anti-theft system in the wiring diagram for the 86-92 series. I checked the W126 CD manual and saw that a YL/BU wire sends a momentary (as long as the key is turned) ground to pin 6 of connector 2. A GN/YL wire sends a momentary ground to pin 7 of connector 2.

If you want to hear from someone who really knows for sure just say so and I'll pipe down :)

I take it project 500TE hasn't begun?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD