SL/R129: testing power window motor
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Junior Member
Joined: Sep 2011
Posts: 15
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1996 sl500
testing power window motor
I'm working on a 1996 sl500 with what I'm told is a bad power top module. The passenger side window works including the feature that drops the window slightly when you start opening the door. When you push the drivers side window switch a quiet click is heard, what I'm assuming is a relay possibly inside the conv. top module . How do you test the power window motor without opening the door panel? Thanks in advance ....Joe
Senior Member
Joined: Nov 2004
Posts: 282
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From: Bradenton, FL
'87 560SL Sold, '99 SL500 For Keeps
Before you get that deep into the module itself, if the driver's side window is fused separately from the passenger side, verify that the fuse is good
Next, I'd swap the switches from the passenger side to the driver's side to determine if the switch is bad
If the window still won't operate, inspect the wiring at the front of the door. I've heard, but not experienced, that the driver's door is particularly susceptible to wiring issues due to opening and closing over time. If wiring looks ok, you may want to remove the door skin anyway, and direct connect to the window motor from a separate 12v source.
If that doesn't produce results, I think it's safe to conclude that the window motor is toast.
If the window motor does engage with a direct elec. connection, next I'd clear the fault codes in the top controller(you'll need someone with the Star Diagnostic Tool) Then see if the window works. If the driver's side begins to work, you may need to re-synch both sides. Doors closed, engine on- Push both window switches down simultaneously and hold them down for a count of 5. Now raise the windows holding both switches down and again count to 5. They're synched.
If you don't have access to Star Diagnostics tool (good independent techs have them) you can try to clear codes by disconnecting the neg side of the battery for at least an hour. Reconnect then synch the windows as above.
Finally, have the codes pulled from the controller to determine controller viability, i.e., the fault codes you deleted will reappear if the controller is the issue.
Good Luck
Next, I'd swap the switches from the passenger side to the driver's side to determine if the switch is bad
If the window still won't operate, inspect the wiring at the front of the door. I've heard, but not experienced, that the driver's door is particularly susceptible to wiring issues due to opening and closing over time. If wiring looks ok, you may want to remove the door skin anyway, and direct connect to the window motor from a separate 12v source.
If that doesn't produce results, I think it's safe to conclude that the window motor is toast.
If the window motor does engage with a direct elec. connection, next I'd clear the fault codes in the top controller(you'll need someone with the Star Diagnostic Tool) Then see if the window works. If the driver's side begins to work, you may need to re-synch both sides. Doors closed, engine on- Push both window switches down simultaneously and hold them down for a count of 5. Now raise the windows holding both switches down and again count to 5. They're synched.
If you don't have access to Star Diagnostics tool (good independent techs have them) you can try to clear codes by disconnecting the neg side of the battery for at least an hour. Reconnect then synch the windows as above.
Finally, have the codes pulled from the controller to determine controller viability, i.e., the fault codes you deleted will reappear if the controller is the issue.
Good Luck
Last edited by BJonesFL; Sep 27, 2011 at 10:01 AM.
Thread Starter
Junior Member
Joined: Sep 2011
Posts: 15
Likes: 0
1996 sl500
After countless delays I finally got around to working on the power windows again. What I found was sticking brushes in the drivers power window motor. After unsticking them it does run but not well. Could be a lack of lube as the car has been sitting a long time now. Funny thing is the drivers window does not respond to the door latch switch or door lock. The window does not drop or raise a quarter inch on opening and closing the door nor does it go up when the door is locked from the outside but the passenger side window does. I may have damaged the hall effect circuit in the window motor. Is there a way to test this other than swapping the passenger side motor? The hall effect system might be ok because it seems to "remember" the max open and closed position when synchronizing. Any input appreciated, Joe.
