The Mercedes-Benz W116, a true icon of automotive engineering, is known for its robust build and luxurious features. However, like any classic car, certain components can succumb to wear and tear over time. One common issue faced by W116 owners is the failure of the power window regulator. In my case, ‘Desert Rose’, my beloved W116, experienced a frustrating driver’s door power window malfunction. The window mechanism had seized, making it clear that a replacement was necessary.
It’s a well-known fact among W116 enthusiasts that the window regulators in these models are susceptible to failure. This is often attributed to the gear mechanism becoming stiff or bound. The regulator bracket, constructed from thin metal, can also warp over years of operation. A contributing factor to this issue is the electric power window motor’s lack of an automatic shutoff. If you continue to hold the window switch even after the window is fully closed or obstructed, it can put undue stress on the bracket. This repeated stress can lead to bending, gear misalignment, and ultimately, the binding and failure of the entire power window system.
Sourcing new front window regulators for a W116 can be a costly affair. To find a more economical solution for ‘Desert Rose’, I turned to the used parts market. I managed to locate a used, but thankfully in good working order (PNP – Pull ‘n’ Pay), window regulator from a 1973 450 SE. Upon inspection, it was evident that this used unit was a relatively recent replacement, indicated by the presence of non-factory access holes already drilled into the door panel – a modification often performed during regulator replacements.
My ‘Desert Rose’, being a 1978 W116 and still sporting its original window regulator, required a modification to accommodate the replacement process detailed in the factory service manual (FSM), job 72-185. This involved drilling three access holes into the door’s sheet metal. These access points are crucial for detaching the electric motor before you can proceed with removing the window regulator itself. Interestingly, my other W116, a 1979 model named ‘Stormcloud’, already had these three access holes pre-cut by the factory, reflecting a later production update to streamline window regulator maintenance. To ensure precise placement for drilling on ‘Desert Rose’, I fashioned a template from corrugated cardboard. This template allowed me to accurately mark the locations for the required access holes on the door panel.
For the drilling itself, I employed my trusty 19mm Milwaukee Hole Dozer hole saw. When drilling these access holes, particularly the lower ones, caution is advised. The curved contours of the door can cause the hole saw to buck or jump. You might also encounter some resistance and potential bucking as the saw transitions into the second layer of welded sheet metal, especially at the frontmost lower hole location.
Once the access holes were drilled, the 5mm Allen head bolts, now accessible through these new openings, were removed. With the motor detached, the old, malfunctioning window regulator could finally be extracted from the door.
Before installing the replacement, I took the opportunity to properly lubricate the window mechanism. I used DeoxIT Marine Mechanical grease on all metal-to-metal contact points of the window regulator. This included the gear teeth, gear shafts, and the regulator arm pivot points. For areas where plastic components would interact with metal, I opted for Sil-Glyde lubricant. Sil-Glyde was also applied to the rubber window channel to minimize friction, the sliding jaw bracket on the vertical guide rail, and the window pane channel where the plastic glides of the regulator arm move. Proper lubrication at these points is essential for smooth, long-lasting operation.
Reassembly was, as expected, a reversal of the disassembly process. With the replacement regulator installed and everything properly lubricated, ‘Desert Rose’ now boasts a fully functional driver’s door window once again. The days of having to open the door just to punch in the parking garage access code are thankfully over! This DIY repair not only saved money but also brought the satisfaction of keeping another aspect of this classic Benz W116 in top condition.
