My 85 500sel passenger side front window went down and won't come up.

I just removed the door panel and confirmed power at the connector. But going down it's like a full 13v and going up it's maybe 8 or 9 volts.

I disconnected the frame and pulled out the motor and it seemed immobile. However, when I pulled the motor off the frame and tested it motor works in either direction when it gets the full 13v and goes nowhere with that 8/9v applied.

Where am I looking next and what am I looking for?

With warm regards,
-CTH

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- cth350@gmail.com
http://www.111lakeside.com/

1) Confirm that when the switch is in "neutral", that both hot legs at the junction block in the door are at battery voltage.
2) Confirm that the ground leg has zero resistance (terminal-to-battery neg.). Note: The ground leg is tested at the switch.
3) If 1 & 2 are OK, and there is low voltage on one hot leg when the switch is actuated, look to the switch for a high internal resistance, or possibly a damaged wire in the harness where it passes thru the door-to-body area.

Thanks Frank. -cth

If Frank’s tests show the switch is good, it could be that the mechanism has too much drag in one direction and that heavy current draw is pulling the voltage down. I sort of remember the 300SD having an issue where the motor was loose. When it twisted in the housing, it would bind and draw high current and run sluggishly if at all. In the other direction, it ran much better but no perfect.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Thanks Michael. I did confirm voltages with the motor disconnected from the circuit and in the circuit and with a different motor in place entirely.

I will back into it on Friday when a new switch arrives. If it doesn't fix the problem, it will, at least, look nicer than the current one, pardon the pun. -cth

-cth

I ordered a pair of replacement switches for the car after not having time to try other things (the originals were worn looking anyway). I popped them in and the low voltage problem went away.

Now to put the window motor back in once the rain stops and ground is less soggy. Hopefully, that's tomorrow AM.

-CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/