How To Fix Mercedes W123 Screw Open Style Window Regulator Repair Guide

Difficulty

Easy

Steps

Time Required

                          10 minutes

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How to fix Mercedes W123 “screw open” style window regulator
9 steps

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Introduction

Age, combined with a certain amount of abuse when using the motor on a regulator that is rubbing, jamming, or skipping can lead to a motor that runs slowly or intermittently. Often, they can be brought back to life with some repair/maintenance. In this guide, you’ll learn to open up one of the two styles of motors; in this case, the motors that open up easily with the removal of a few screws. Once open, the electrical motor can be cleaned and the gears can be re-greased and you can likely get several more decades of use out of your motors!

What you need

Step 1

              How to fix Mercedes W123 "screw open" style window regulator

To access and perform maintenance and repair on your power window regulator motors you will of course first need to remove the regulator. For the rear window regulators, click here to review the removal guide.
You will then need to remove the motor from the regulator by first removing the three 10mm bolts that attach it in place.

To access and perform maintenance and repair on your power window regulator motors you will of course first need to remove the regulator. For the rear window regulators, click here to review the removal guide.

You will then need to remove the motor from the regulator by first removing the three 10mm bolts that attach it in place.

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Step 2

Before starting this guide, confirm that you are reviewing the guide for the correct motor type for your situation. This guide covers the “Screw Open” style of motor, as seen on the right. If you have a “Drill Open” style of motor as seen on the left click here to review this guide instead.

Before starting this guide, confirm that you are reviewing the guide for the correct motor type for your situation. This guide covers the “Screw Open” style of motor, as seen on the right. If you have a “Drill Open” style of motor as seen on the left click here to review this guide instead.

Step 3

Remove the three flat-head screws on the rear cover of the gear housing.

Remove the three flat-head screws on the rear cover of the gear housing.

Step 4

Using a flat-blade screwdriver or other appropriate tool, pry the cover off the back of the gear housing and set it aside.
There is a plastic gasket between the housing and the cover, so you’ll want to watch for that and set it aside with the cover.
With the cover removed you’ll see:
The worm gear that the electric motor turns and,
The main gear the turns the outer gear which then moves the regulator

Using a flat-blade screwdriver or other appropriate tool, pry the cover off the back of the gear housing and set it aside.

There is a plastic gasket between the housing and the cover, so you’ll want to watch for that and set it aside with the cover.

With the cover removed you’ll see:

The worm gear that the electric motor turns and,

The main gear the turns the outer gear which then moves the regulator

Step 5

Pull the black plastic electric motor cover away from the gear housing. It does not attach, it’s held in place by friction, so a steady pull should move it.

Pull the black plastic electric motor cover away from the gear housing. It does not attach, it’s held in place by friction, so a steady pull should move it.

Step 6

Place the electric motor portion of the device over a container that can catch drips as you clean it.
Thoroughly spray the motor with electrical cleaner.

Place the electric motor portion of the device over a container that can catch drips as you clean it.

Thoroughly spray the motor with electrical cleaner.

Step 7

Inspect the gears, especially the large plastic gear, for severe wear such as broken teeth. This would lead to needing a new or good used motor. If they look like the one on this motor, they can simply be re-greased.
This particular motor would definitely benefit from a good greasing; you can see that there is not much grease left and what is there is clumped in one area.

Inspect the gears, especially the large plastic gear, for severe wear such as broken teeth. This would lead to needing a new or good used motor. If they look like the one on this motor, they can simply be re-greased.

This particular motor would definitely benefit from a good greasing; you can see that there is not much grease left and what is there is clumped in one area.

Step 8

Use a good synthetic grease, like silicone based SuperLube. Do not use petroleum based greases like vaseline or moly grease as oil based products can damage plastic and rubber parts.
Use your finger or, better yet, a grease syringe to thoroughly lubricate the plastic gear teeth and the worm gear.

Use a good synthetic grease, like silicone based SuperLube. Do not use petroleum based greases like vaseline or moly grease as oil based products can damage plastic and rubber parts.

Use your finger or, better yet, a grease syringe to thoroughly lubricate the plastic gear teeth and the worm gear.

Step 9

Before re-installing the cover, apply a small amount of silicone grease to the plastic gasket to help it re-seal well.

Before re-installing the cover, apply a small amount of silicone grease to the plastic gasket to help it re-seal well.

To reassemble your device, follow these instructions in reverse order.

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                    Nicolas Siemsen

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Pedro Lanhas - Apr 19, 2018

Hello, thanks for the information; I happen to have problems in the front, not the rear window. The motor (screw open) runs ok, but I will give it a clean up and lubricate it as seen here; Any hints on how to remove it from the car, with the rest of the linkage mechanism? same as in the rear?

Thank you,

Pedro, from Portugal. pedrolanhas@gmail.com

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