Power windows

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Power windows

Postby stuartm » Sun 30 Jul, 2017 11:21 am

I have a 76 450SLC. With a door open all electric windows work perfectly.
With the doors shut the windows will not operate at all.
The centre safety button locking the window buttons in the back seats works as it should.
The problem appears to be somehow linked to the buttons in the doors controlling the footwell lights.
Once one of these buttons is depressed, by the door or by hand, the windows stop operating.
I'm puzzled by why or how the footwell lights affect the power supply to the window motors.
Can anyone advise?
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Re: Power windows

Postby Chai » Mon 31 Jul, 2017 10:38 pm

You didn't mention whether the ignition was on/engine running at the time of this test. If the engine was off - your windows are operating as designed.

The purpose of the interior light switch is to allow the opening/closing of the windows when the engine is stopped (ignition is OFF) AND the door is ajar.
With the ignition key ON, the windows will operate regardless of whether the door is ajar or not - using the buttons on the console (i.e. ignore the back seat window controls as it's affected by the disable switch).
Finally, if the ignition is OFF AND the door is shut, the windows will not operate.

The designers added this feature as a convenience, say, to the seated passenger when the driver is filling the fuel tank. Most lesser cars built into the 1990s requires the ignition ON to operate the windows.
1974 450SLC
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Re: Power windows

Postby Lance » Mon 31 Jul, 2017 11:47 pm

Well thank you Chai, I have just learnt something new, this also applies to my W123. I had to run out and check it as soon as I read your post. I always thought that I had once closed the window with the ignition off, obviously I had the door open at the time. I couldn't work out why I couldn't do it again, I just assumed I was mistaken or I had the ignition on.
A very convenient feature.
Lance Smart

W114 280E 5 speed manual
W123 280E
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Re: Power windows

Postby stuartm » Sun 13 Aug, 2017 3:04 pm

Thanks for the replies to my query.
I had another problem occur when I lost the instrument gauges. (Tacho, oil, temp and fuel).
I tracked this to a blown fuse.
My German is non-existent but it appears there are two fuses named for the instruments on the cover to the fuse box.
The fuse in the top row was blown and when I replaced it all gauges worked - and the windows worked as they are supposed to.
All problems now fixed.
Thanks for your comments
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