Classic Mercedes Maintenance: Repairing Window Regulator Guides

Replace the broken plastic guide and not the whole regulator. I got the replacement slide from Partsgeek. Peachparts and some other online retailers also carry them. Here is one of them. https://www.pelicanparts.com/More_Inf... In this technical tutorial from Stray Benzes, Ralf demonstrates a cost-saving repair for a common failure in the Mercedes-Benz W126 S-Class: the broken plastic window regulator guide. Instead of replacing the entire regulator assembly, which can be expensive, he shows how to replace just the plastic slide using a few simple tools. Video Indexing (Chapters) [00:00] Introduction: Identifying a non-working rear window on a 420SEL. [00:30] Diagnosis: Discovering the busted plastic slide inside the door. [01:30] Disassembly: Removing the regulator and window motor. [03:11] Preparation: Drilling out the old rivet from the regulator arm. [03:56] The Repair: Installing and flaring the new plastic slide "rivet." [05:15] Reinstallation: Lubricating the arm and seating the regulator. [06:24] Alignment: Sliding the new guide into the window's metal groove. [08:11] Functional Test: Verifying smooth window operation. [09:01] Maintenance Tip: Inspecting the door check strap for rust and wear. Video Summary Ralf identifies that when a rear window stops moving, it is frequently due to a failed plastic guide rather than a motor failure. While a full regulator assembly can cost over $100, the individual plastic inserts are available for a few dollars, allowing for a durable and economical repair. Key Technical Highlights: Identifying the Culprit: Upon removing the door panel, Ralf finds the plastic componentry of the regulator slide has shattered. This part is responsible for traveling within the window's horizontal metal track to lift and lower the glass. Drilling and Riveting: The original guide is held in place by a metal rivet. Ralf demonstrates drilling out this rivet to clear the arm for the new part. The replacement guide includes a new pin that must be flared open using a center punch and hammer to create a secure, permanent attachment to the regulator arm. Lubrication: Before reassembly, it is critical to clean off old, hardened grease and apply fresh lubrication to the regulator's slide and the window's track. This reduces friction and prevents the motor from straining. Installation Hack: To align the new slide into the window groove, Ralf uses the window switch to move the regulator arm into a specific position that allows the guide to be inserted into the end of the window's metal track. Secondary Inspection: While the door is disassembled, Ralf recommends checking the door check strap (the mechanism that holds the door open). He notes that these are prone to rust and can lock up or snap, potentially damaging the door shell if not maintained. Video URL:    • Classic Mercedes Maintenance: Repairing Wi...   YouTube Channel: Stray Benzes