Fix the Alarm in your w124, w126, w201, w202, r107, - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 1 (permalink) Old 03-21-2008, 08:18 PM Thread Starter
BenzWorld Junior Member
Date registered: Sep 2007
Posts: 43
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
Fix the Alarm in your w124, w126, w201, w202, r107,

1: Is your Mercedes Alarm Working ? - Test it!

Mercedes Factory Alarm on w201,w124,w126,r107: The original Mercedes factory alarm is way better than most any after market system available out there, as it has sensors all over the car, and will shut the engine down if triggered, and flash the Head lights. Most after market alarms are nothing more than motion sensors which trigger all the time to sub-woofers of passing cars.

Many previous owners disabled the Mercedes factory alarm systems on these older Mercedes models due to false alarm triggering when UN-LOCKING the car with the key.The false alarms are usually caused by worn micro-switches on the door lock barrels, and usually there is nothing wrong with the Mercedes alarm module.

There are only alarm Micro-switches in the Driver and Passenger doors (and on the tailgate in a TE/TD wagon). On all sedans, there are NO microswitches in the trunk, and the alarm is controled from the central locking vacuum pump control line. This is why if you are having trouble with your alarm, Un-Locking the car from the trunk / boot will not cause false triggering, while Un-Locking it from the driver or passenger door will.

Usually installing a remote keyless entry system in the trunk / boot will overcome your alarm problems, as you no longer need to unlock your car with the key, and thus avoid using the alarm microswitches in the doors. Any keyless entry system will work.

If the alarm module was disconnected, you could try re-connecting it. If it was just the micro-switches causing the problems, you will be able to control the alarm with the keyless entry system and overcome the problem..

So you might want to check your factory alarm is connected and working. .........

Here is how to test :-

With the car windows open, but the doors, hood and trunk closed, centrally lock your car either with the Keyless Entry (if installed in the trunk) or with the key from the TRUNK. Then put your hand in the open window and open the lock by hand, and open the door, then put your key in the ignition and turn the key. By now your alarm should have activated by either the door trigger or the ignition switch trigger. (Headlights will flash, and loud Alarm horn will sound).There are also other triggers on the hood and trunk and extreme motion sensor.

To stop a triggered alarm, un-lock the TRUNK with the key (as door micro switches may not work), or the kryless remote control if it has been installed in the trunk. (If keyless system is installed in the trunk, do all testing of alarm with the remote fob).

If you can’t start the car, and the headlights are flashing, then the factory alarm got triggered, but the alarm horn has been disconnected under the hood. (Probably as the previous owner got fed-up with the sound of it). You should re-connect the alarm horn under the hood, once you have the keyless system installed in the trunk, as there is probably nothing wrong with your alarm. The Alarm horn is situated near the ABS unit in the engine.

If your alarm did not activate during this test, then your Mercedes alarm module has been disconnected or removed, or is not functioning. Apparently on the very early models, the alarm was an option, so maybe your car never had one. You will find the Mercedes alarm module under the foot well on the front passenger side. Lift the carpet up and you will see a plastic panel. Remove that panel, and it should be there. If the alarm system has been disconnected, it was probably un-plugged here at the alarm module. (In soft-top w124 convertables, the Mercedes alarm module is situated in the trunk on the passenger side)

Another problem encountered with the Mercedes factory alarm is it will activate when you LOCK the car from the Trunk or Drivers door or Passenger door. (Trunk is best test but, you need to try them all). If the alarm triggers as you LOCK the car, you need a replacement alarm module. Used alarm modules are approx $25 at wrecking yards where you pull the parts yourself.

When you install the keyless entry unit in the trunk, you connect it to the three central locking control lines that go to the trunk actuator. You can either splice into those three control wires, or you can get the correct Mercedes electrical plug from a wrecking yard, which will plug into the trunk actuator control line. If you use a Mercedes plug at the actuator, you don't end up damaging or changing your cars wiring harness in any way. It all stays original. (In the trunk you power the system from the Trunk light).

Any keyless entry system on the market will work, as they all basicly work the same way. Just make sure you install it in the trunk, as that way it will also control your factory alarm. (If you install it in the drivers side kick panel, as all manufactures recommend, it will NOT control the factory alarm without additonal external relays, that's why the trunk is the best).

So if you want a cheap keyless system from your local Auto Store, they will all work. But if your are after a Mercedes style remote fob, I offer those at resonable prices, and include the Mercedes electrical plug you need to plug it into the trunk actuator, thus making it Plug-and-Play. If you're intersted in my system visit Mercedes Benz Plug In Keyless Entry Upgrade where you can find the correct electrical connections. But any system will work, so you don't have to buy mine.

NOTE: You do not need an Mercedes Factory Alarm to install a Keyless entry system in your car.

DID YOU KNOW: If you lock your car with hood open, then disconnect the battery, when you go to reconnect the battery the Mercedes alarm will trigger. This means you can leave your car parked and un-attended or months with battery disconnected, and if anyone tries to steal it, the alarm will trigger when they hook up the battery.
davidknaus is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Similar Threads
Topic Author Forum Replies Last Post
kEYLESS UPGRADE for w124,w126,w201 davidknaus For Sale/Wanted/Trade/Giveaway 16 04-11-2011 12:27 PM
PLUG-IN Keyless entry W/ Flip-Out Key remotes w124,w126,w201,w202,r107 davidknaus For Sale/Wanted/Trade/Giveaway 14 07-24-2010 11:53 AM
FS: REAR CAMBER KIT fits: R129 SL R170 SLK W201 W202 W203 C W208 W209 CLK W124 W210 E deyainrdy4ds For Sale/Wanted/Trade/Giveaway 5 01-20-2008 09:24 PM
Vintage AMG badge for sale w116,w123,w201,w124,w126 coupe For Sale/Wanted/Trade/Giveaway 1 10-03-2007 09:30 AM
need power window motors for W201,W126,W124? Guest (MBNZ) General Mercedes-Benz 0 02-25-2002 05:59 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Title goes here

video goes here
description goes here. Read Full Story
For the best viewing experience please update your browser to Google Chrome