For owners of a classic W116 Benz, a common frustration can be the power windows, particularly when they start to stick or fail entirely. In my experience working with these iconic vehicles, the window regulators are often the culprit. Recently, the driver’s side window on my W116, affectionately nicknamed ‘Desert Rose’, decided to give up the ghost. The mechanism had seized, making a replacement necessary. This is a repair many W116 Benz enthusiasts can tackle at home, and this guide will walk you through the process.
Understanding W116 Window Regulator Issues
Window regulators on the W116 Benz are known to be susceptible to failure. The primary reason is the design of the gear mechanism, which can bind over time. The bracket itself is made of relatively thin metal, and years of operation can cause it to warp. A key factor contributing to this issue is the lack of an automatic shutoff for the power window motor. If you continue to hold the window switch after the window is fully closed or opened, the motor keeps applying pressure. This repeated stress can bend the regulator bracket, misaligning the gears and leading to the mechanism binding and eventually failing.
Step-by-Step W116 Window Regulator Replacement
Finding new W116 front window regulators can be expensive. To keep costs down, I sourced a used, but thankfully newer replacement regulator from a 1973 450 SE. It was clear this was a later replacement part due to the presence of non-factory access holes in the donor car’s door. My ‘Desert Rose’, a 1978 model with its original regulator, required the creation of these access holes. These holes are essential for removing the electric motor before you can take out the window regulator itself, as detailed in the factory service manual (FSM) job 72-185.
http://handbook.w116.org/Chassis/72-185.pdf
To ensure accurate placement of these access holes, I created a template using corrugated cardboard, mirroring the factory-made holes found on my 1979 W116 ‘Stormcloud’, which already has these updated access points.
Alt text: Cardboard template positioned on a W116 Benz door panel, marking locations for drilling access holes to facilitate power window regulator replacement.
Using a 19mm Milwaukee Hole Dozer hole saw, I carefully drilled the three access holes in ‘Desert Rose’s door sheet metal. Exercise caution, particularly when drilling the lower holes, as the saw can buck due to the door’s curves. Be prepared for a potential buck as the saw transitions into the second layer of welded sheet metal, especially at the frontmost lower hole.
Alt text: Close-up of a hole saw drilling into the door panel of a W116 Benz, creating an access hole for power window regulator service.
Once the access holes were drilled, the 5mm Allen head bolts holding the motor were accessible and removed. After disconnecting the electric motor, the damaged window regulator could be taken out.
Before installing the replacement, proper lubrication is crucial. I used DeoxIT Marine Mechanical grease on all metal-to-metal contact points of the regulator, such as gear teeth and shafts, and the regulator arm pivot. For areas where plastic parts contacted metal, I used Sil-Glyde. Sil-Glyde was also applied to the rubber window channel, the sliding jaw bracket on the vertical guide rail, and the window pane channel for the regulator arm’s plastic glides. This comprehensive lubrication ensures smooth operation and prolongs the life of the regulator.
Reassembly was simply the reverse of disassembly. With the replacement regulator installed and properly lubricated, ‘Desert Rose’ now boasts a fully functional driver’s side power window. The convenience is back – no more rolling down the window manually, and definitely no more opening the door just to enter the parking garage access code! This DIY repair not only saved money but also restored a key feature of this classic W116 Benz.
