Mercedes W123 Disable Security Alarm Repair Guide

Difficulty

Very easy

Steps

Time Required

                          10 minutes

Sections

Mercedes W123 disable security alarm
4 steps

Flags

Member-Contributed Guide

An awesome member of our community made this guide. It is not managed by iFixit staff.

BackMercedes W123
Full Screen
Options
History
Save to Favorites
Download PDF
Edit
Translate
Get Shareable Link
Embed This Guide
Notify Me of Changes
Stop Notifications

Introduction

Step 1

              Remove floormats

Remove passenger (right) floor mat(s). Mine had the sound deadening one plus a protective one over the top of that.

Remove passenger (right) floor mat(s). Mine had the sound deadening one plus a protective one over the top of that.

1024

Step 2

              Remove plastic kick plate from right footwell area.

Remove passenger side (right) plastic kick plate. You must move it up to disengage the metal hooks in the car body from the plastic kick plate clip points (one lower, two upper). Tilt the panel counter-clockwise and remove toward rear of vehicle. Takes a bit of patience to manuever it effectively to tilt backward and free from footwell area.

Remove passenger side (right) plastic kick plate. You must move it up to disengage the metal hooks in the car body from the plastic kick plate clip points (one lower, two upper). Tilt the panel counter-clockwise and remove toward rear of vehicle. Takes a bit of patience to manuever it effectively to tilt backward and free from footwell area.

Step 3

              Disconnect security alarm relay

Disconnect battery ground strap. You might be able to skip this step if you are confident and careful not to do amatuer arc welding of potentially hot wires in these harness plugs. I got by without doing this step your mileage and skill may vary.
Disconnect the two multi plugs from the alarm relay. These are fairly stubborn to disconnect. Requires a bit of pressure to remove.
I apologize for the fuzzy photo of the wiring harness but I was not able to get a clear shot. The second shot is a closeup of the relay after it is physically removed. I took that step because I don’t want this thing annoying me while trying to drive the vehicle ever again.
The relay is attached to the kick panel with typical plastic movable core rivets. You can push the core out with any handy tool (I used a pocket knife blade). Mine had only one but hey this is a 31 year old car!!!
If you leave it attached to the kick plate you might want to tape over the harness ends somehow so they can’t short against those exposed pins.
I understand later models of mercedes vehicles use the same relay but also have an additional relay in the dashboard that disables starting the engine. If you google you can probably find instructions for how to work around that “feature”. I will not cover that here because I have no vehicle to provide photo context.

Disconnect battery ground strap. You might be able to skip this step if you are confident and careful not to do amatuer arc welding of potentially hot wires in these harness plugs. I got by without doing this step your mileage and skill may vary.

Disconnect the two multi plugs from the alarm relay. These are fairly stubborn to disconnect. Requires a bit of pressure to remove.

I apologize for the fuzzy photo of the wiring harness but I was not able to get a clear shot. The second shot is a closeup of the relay after it is physically removed. I took that step because I don’t want this thing annoying me while trying to drive the vehicle ever again.

The relay is attached to the kick panel with typical plastic movable core rivets. You can push the core out with any handy tool (I used a pocket knife blade). Mine had only one but hey this is a 31 year old car!!!

If you leave it attached to the kick plate you might want to tape over the harness ends somehow so they can’t short against those exposed pins.

I understand later models of mercedes vehicles use the same relay but also have an additional relay in the dashboard that disables starting the engine. If you google you can probably find instructions for how to work around that “feature”. I will not cover that here because I have no vehicle to provide photo context.

Step 4

              Reassembly

Reassemble kick plate being careful to make sure the harness is protected from shorting against anything.
Reinstall floor mat(s).
Reattach battery ground if you disconnected it for safety.

Reassemble kick plate being careful to make sure the harness is protected from shorting against anything.

Reinstall floor mat(s).

Reattach battery ground if you disconnected it for safety.

Enjoy the sound of silence.

Cancel: I did not complete this guide.

                                                                                      2 other people completed this guide.

Author

                                      with 1 other contributor

                    tcagle53

Member since: 06/18/2014

7,816 Reputation

                                      10 Guides authored                  



                       Badges:
                       29







                                                        +26 more badges

Team

                       Chromebook Cowboys                        

                                                  Member of Chromebook Cowboys 



                    Community                     


                                            2 Members                     


                                            21 Guides authored

Member-Contributed Guide#

Introduction#

#

#

#

#

#

#

Team#

#

Member-Contributed Guide

Introduction

Team