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Old 09-04-2003, 11:07 PM
DanielW DanielW is offline
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Join Date: May 2001
Posts: 161
Outcome of seat switch repair, 87 300E

Hello Group,

I thought I should inform anyone who might have followed this thread (or later searching for "seat switch" problems) know what I found out. Don't understand everything I came on but will give you an account.

I repaired my old switch by cleaning each of the 17 contacts and carefully reassembled switch and it worked problems!

1. The little "seat" shaped buttons must come off 1st. They just push on and off. I used two small flat screw drivers to get behind them and lever them off. Using two tools , one on each side allowed the buttons to come off straight without risking twisting which could have broken them or the post onto which them push.

2. Then the trim bezel surround piece can be carefull worked off with the same flat blade screwdrivers or any flat thin blade. I used a large round pointed pocket knife blade.

3. Locate and remove the two phillips head screws one on Right and one on Left. Use of a MAGNETIC tip screw driver bit is a good idea since you will not be able to reach into the small area with you finger tips to remove the loosened screw. Don't DROP it because it might fall down into the door cavity and who knows what it might lodge on!! Window track gear teeth come to mind, and you won't want to take off the entire door panell to extract it.

4. Use a plastic on non conductive flat wooden strip to lever up the (3) wiring harness plugs. I discovered that there is voltage on some of the wires all the time, key on or off. Don't short circuit the plug posts.

This is where I found something which I don't quite understand. Measured voltage running the motors on mine was 1.47 volts. Or is that just a low control voltage used to make the switches last longer?? Perhaps this voltage triggers relays down on the engines; but thought it unlikely that the engines actually operate on such a low voltage.

5. Take the switch in to a clean work table. Remove the single phillips screw from the middle of the back, then laying it in position with adjustment posts UP on white terry towel. Use a small flat screw driver or small blade pocket knife to carefull pry up and lift the top cover at the 8 or so plastic lock tab spots. Do this very slowly and evenly and don't turn the unit over after you begin to get the cover partially off since there are MANY parts could then begin to fall out. Thats what the terry cloth was for; to catch the 17 steel balls and many assorted small brass parts which could fall out and roll off your work surface and onto the floor. The idea is to do it slowly so NONE of the parts fall out. You want to see and understand how everything works. Sketch it perhaps before dissembly. There is no need to take out the springs, but you will need to lay aside each of the balls that rest on top of each spring.

6. The only thing I had to do was clean top and botton contact points of the 17 toggle type switches. They are under the brass tabs that lay in slots. I used 600 grit wet or dry sanding paper rolled into a very small tube so I could "polish" off the burned or tarnished contacts. You will have to use a sharp tipped knive or similar tool to lever up one of (2) locking tabs on the center toggle unit. You can just lift out the other (3) toggles but that center one is secured down.
The heat rest toggle works differently but very simply. The (1) ball bearing itself carries the electrical current on that one -- so be sure the ball is down under the spring and free to roll back and forth toward the two little posts which you have polished clean.
After all cleaning of contacts you assemble all the toggles. There are balls at top and bottom of each little tube. I used a small dab of silicon electrical bulb grease to hold the balls on top of each spring. Also used it to lube each of the small tubes on which units pivot. This type of grease will not hurt the contacts function even if it were to get on the contacts, but I figure the contacts were dry originally.

7. Align and visually check all the little brass tabs which had the contacts you cleaned, are they flat in their slots? All the balls in place? Press the cover down and it locks in place. Screw in the phillips on the back. Test each of the switches for physicall movement. If OK put in back in your car and use another 200K miles . There is nothing which shouldn't work if you didn't break or lose a part. Good luck. I hope you will be able to save the $85 or so on parts and who knows how much labor a repair shop would tack on the a 15 minute or less simple parts swap.??

My car is an 87 300E with 198K miles, so the switches are lasting quite a long time before needing any attention.
I was impressed with the elegant way the parts function. I know these instructions sounds complicated but that not really the case. If you take your time you will see how it all works, and the nice thing about it is I don't think it will assemble but one way so you can't put the cover on if all the parts are not in there right. Don't force anything.
I wish is had a digital camera.... a picture would describe this much easier.
Go for it .... even in worse case you might have to buy the switch anyway.
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