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Old 11-25-2002, 11:42 AM
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Question 85 MB 300 DT - Power window switch

I've been having problems with the front and rear power passenger (right) side windwows. Occasionally they operates but mostly don't.

The rocker switches (F&R) lit, so the current must be passing through. My first suspicion is that the switch must have bad contact, but I wonder how this can happen to both both F & R? The probably cause then appears to be that the switch may be bad. Therefore, I tried using the driver (left) side switch which is good, to power up and down the malfunctioned windows. Surprisingly, this doesn't work either. After all efforts, I restored everything back to the way they should be, the malfunctioned windows beccame operational again. The cold front is coming so I decided to leave them alone for now, but I am puzzled...

My questions: is there a kind of chemical I could apply to the switch and the plug to make them more contact sensitive? Can the driver side switch work on the passenger side switch (given that the driver side switch has a locking mechanism which I did not unplug)? Is the most likely that the problem can be solved by replacing the passenger side switch with a new one?

Thanks for any assistance you can provide.


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Old 11-25-2002, 12:48 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
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Try replacing OR "turning" the fuses for the power windows in the fuse box.
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Old 11-25-2002, 06:03 PM
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Thanks for your advice. I've checked the fuse box yesterday and I don't recall that among a about 14 fuses, any was marked for Power Window or right front power window, right rear power window... Since my problem is with both the right F & R window, I presume shey share 1 fuse?

I'll take a look at the fuse box again.

Thanks again!

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Old 11-25-2002, 07:08 PM
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Join Date: Dec 2000
Location: Boston area
Posts: 31

I just did this repair on my '85 300TDT. The console switches are not the same from drivers side to passengers side, so swapping them doesn't do anything useful. You can carefully pry them open, one at a time and clean them with good contact cleaner. this sounds like it should work for you.

If not then buy a new set thru FASTLANE.

Remember, the drivers side front and the passengers side rear on the same fuse circuit, as is the drivers side rear and the passengers side front.
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Old 11-25-2002, 07:22 PM
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Location: San Francisco, CA
Posts: 3,097

Clean your switches .... it isn't hard and I bet that might be the problem ....

Pull your switch assembly and note the wiring. Take the switches a part carefully. They almost never wear out, they are almost always full of debris ....

Remember that inside there are tiny springs and little ball bearings ....

I have done this several times and using a towel on the table really helps keeping the little parts from getting lost.

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Old 11-25-2002, 09:35 PM
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Thanks to you all. Have a great Thanksgiving.
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Old 11-25-2002, 09:41 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
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I can't agree more with haasman - I have seen too many of those little balls roll away after I have pried these switches apart. Either do it over the towel like he says or do it over an open shoe box.
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Old 04-23-2007, 03:43 PM
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Window switch secret

One thing I discovered while cleaning a rear window switch on my '87 is that the current to the window motor goes through the rear switch. The rear switch must be present and working for the window to work, even using the front switch for that window. The switch contacts get dirty from many years of sparking as you use the switch and the front switches also get dirty from stuff getting spilled on the console.

The switches are easy to --carefully -- pry open and clean. Always mark or otherwise record the position of the rocker arm relative to the switch body so you get it back together correctly. The advice to do the work on a towel or over a small box is sound -- those little ball bearings can get lost so easily. Once the switch is apart, tip it over and dump the ball bearings onto the towel. If the rocking metal contacts don't also fall out, you can lift them out and clean them with a relay file or fine sandpaper.

When you reassemble the switch, remember that the rocker will go in upside down just as easily as it will go in the right way. If you get the rocker backwards, the switch will appear upside down -- the pins are offset so they won't go on the cable upside down. That's why you were careful to mark the switch before you took it apart (you did remember, didn't you?).



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