Mercedes W126/W124 Power Seat Troubleshooting: Part 1 - Main Power Fix

In this first installment of his power seat series, Ralf from Stray Benzes covers the initial diagnostic steps for when power seats in classic Mercedes models—specifically the W126, W124, and W123—stop functioning entirely. He explains the vehicle's electrical logic and how to quickly rule out fuse issues. Video Chapters [00:00] Introduction: Overview of power seat systems in the W126, W124, and W123. [00:44] Operating Logic: Understanding when the seats should (and shouldn't) move. [01:32] Technical Setup: Using a multimeter to test for DC voltage. [01:44] Fuses A & B: Identifying the primary power source for the memory seats. [02:27] Diagnosis Logic: Differentiating between total power failure and single-seat faults. Video Summary Ralf emphasizes that the first step in troubleshooting is understanding how the system is designed to work. In these classic models, the power seats should always operate when the door is open, even if the key is not in the ignition. If neither seat responds under these conditions, the problem is likely at the source of the power supply. Key Technical Highlights: Testing Fuses A & B: These two fuses are the primary culprits for total system failure. Ralf demonstrates using a multimeter set to DC volts to check for power at these points. The "Door Open" Requirement: When testing fuses A and B, the door must be open. If the door is closed and the key is out, you will likely see no voltage; opening the door completes the circuit and should show a full 12-volt reading. Isolating the Fault: If both front seats are dead, it points to a blown fuse or a main power supply interruption. However, if only one seat fails while the other works perfectly, the main power is fine, and the issue is likely a faulty door switch or memory seat control module. Memory Seat Considerations: Ralf notes that memory seat functions are often "used and abused" and are the first things to check if the mechanical operation of the seat remains intact but the preset functions fail. Video URL:    • Mercedes W126/W124 Power Seat Troubleshoot...