Introduction

Yesterday, I followed some tips found elsewhere on the internet to disable the security alarm on my 1985 300sd MB. After driving over 30 miles in suburban traffic with the intermittent sounding of the annoying horn and light show the whole way it was time for this "system" to go. This is for a US market 300sd others may vary.

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.

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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.
  • 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.

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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.
  • 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.

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  • 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.

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Conclusion

Enjoy the sound of silence.

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tcagle53

Member since: 06/18/2014

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