1992 Mercedes SL window motor running continuously
TheSaint’s 1992 R129 developed a passenger window that lowered itself and would not close. Later checks and a telephone consultation pointed the owner toward the roof controller, but no completed repair was reported.
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A window that opened by itself
TheSaint describes finding the right-hand window of a 1992 SL open after parking the car. The door mechanism appeared secure, and the window briefly worked with the trim removed. After an overnight battery charge and reconnecting the negative lead, it lowered itself again. Pressing the close switch produced a click, with another sound repeating roughly every five seconds. Recent work reconnecting loose wires at the N10/2 combination-relay connector prompted a separate request for the correct R129 pin assignment.
The later checks changed the clicking explanation
With the trim removed again, the owner identified both sounds as coming from the window motor. The motor kept trying to lower an already open window while the battery was connected. Holding the close switch stopped the motor; releasing it made the motor run again. Manually operating the limit-switch microswitch did not stop it, and removing the N10/2 relay did not change the symptom. These are the owner’s observations, rather than a validated diagnostic sequence or instructions for bypassing the controls.
A controller diagnosis, with the outcome still open
TheSaint later reports that a technician from The R129 Co, consulted by telephone, also attributed the problem to the roof controller. The owner then added that the roof had not been operated in almost ten years, and planned to remove the hardtop and try cycling the soft top before investigating the controller. The thread does not report that attempt, a controller repair or replacement, or restored window operation. The suggested controller diagnosis remains attributed to the owner and telephone consultation. A W140 connector diagram posted earlier was explicitly a reference for the pin-assignment question, not a verified R129 wiring diagram.