Bad W126 window regulator

Another long standing to-do list item on my 300SE was the passengers side window.   Over time, the window would slip down so there was half a centimeter gap at the top.   It would also make a clunking sound at the top of the window travel.

I had purchased a good used W126 window regulator a couple of years back.   Yesterday I decided to try and fit the regulator.   To get to the W126 window regulator, the door card must be removed.     To do so, there a few screws holding it in place.    Two holding the little chrome embellisher near the door striker,  one behind the plastic backing for the door pull and three for the arm-rest.     Once the screws are out, the door card lifts up and out.   Many of these are damaged when people attempt to just pull it outwards.

Behind the door card is a moisture barrier.   Mine was in a sorry state.

I will replace this after I get the window regulator working properly. Next step was to check why the regulator wasn’t working properly. A quick test confirmed the behavior I had seen.

When I took a closer look at the mechanism, it was pretty clear why the motor was jumping like that.   The regulator was missing multiple teeth.

I wasn’t able to replace the regulator as the used unit I had was quite different to what was installed in the car.   Doing further research, it turns out it is for a coupe.    This isn’t so bad as having a coupe spare is quite useful as they are now hard to come by.

Looking at the parts catalog there are two regulator types possible for my car.   The first type was made by Brose and has part number 126 720 13 46.   I have this type on my car.   The second was made by Reitter & Schefenacker and has part number 126 720 17 46.   I understand the main difference is the number of teeth on the motor.   Therefore the difference doesn’t matter if you’re going to swap the regulator and motor as a unit.

While I was doing this job I noticed another wiring harness in the door.   It even had the little Mercedes-Benz pin connectors, so it was unlikely to be aftermarket.   Most aftermarket radios and alarms I have found in these cars were quite sloppily installed with the wires just twisted together.

I started a thread on the ozBenz forum and it turns out that it is likely from option code 551, which was the anti-theft system.   An unusual option for a low spec 300SE like this one.

I’ll leave the door card off while I source the new regulator.   It sure makes a difference to road noise though.