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Old 12-28-2014, 11:11 PM
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'Evil' Servo Restoration Aluminum 21 step program (many images)

This thread would never have been possible without the Aluminum servo that unkl300d sold to me. Thank you very much!
Also It would have taken significantly longer to understand how to properly disassemble and reassemble the entire servo, had it not been for the help of this thread http://www.peachparts.com/shopforum/vintage-mercedes/245876-evil-servo-rebuild.html

Now with any rubber that is 34 years old it tends to wear out. In this case the housing was leaking because the rubber had been exposed to 80-100c temperatures for 34 years, understandably it might start to leak. (scroll to the end for cracked housing theory)

See this thread for the difference between the OEM Aluminum and Plastic Servos http://www.peachparts.com/shopforum/vintage-mercedes/205757-accii-climate-servo-102-104-a.html
Now for the meat of the thread. I had originally tackled this project, however the spring was caught causing the valve to stay closed. Therefore, I decided to open the servo up again. (among the fact that my Auxiliary water pump was inoperable.)

This project was very inexpensive maybe $15-$20?
-Napa 765-1237 High-Temp RTV Silicone Gasket Maker
-Ace hardware for the four main screws in the bottom, as well as the two smaller screws for the vacuum connection.
-WD-40
-Phillips Screwdriver
-Small Screwdriver
-9v battery and 10-12 gauge wire
-Razor Blade (for scrapping and crud)
-Newspaper/cardboard
-desk and chair
-small bright light
-Dielectric grease (optional)

Step 1: Use the cardboard as a mat to work on or newspaper. Remove the top cover of the Servo, 4 small screws.



Step 2: Before we go through this whole process, you will want to test the motor inside the servo. If the motor is fried, your best bet is either a new servo, or find a used one, and you may need to piece it together. The motors from the aluminum and plastic servos are interchangeable. Tape one end of the wires to the battery, with the other end of the wire attach the positive to the brass connector with the orange wire, and the negative to the blue wire brass connector. Let it go to one end completely, then flip the wires and run it back.

Step 3: Remove the next four screws that hold the Rubber plate to the aluminum housing, exercise caution, as the two orange and blue wires go directly to the motor, and the cap may pop off (happened to me explained latter) I used the Servo cover and rested the rubber plate against it to prevent it from pulling on the wires.



Step 4:Gently lift up on the metal plate a screwdriver may come in handy, there is nothing holding it in place, it simply has a snug fit. Lay the Rubber and metal plate to the side without stretching the wires.


Step 5: Remove the spring with the piece mounted at the top, lay to side. Unscrew the center pin and lay to the side, if the washer and bearings remain, remove those two and lay to the side. Put the spring on top of the pin, with the pin inside the washer and bearing, off to the side.




(I removed the washer after the photo was taken.)


Step 6: Now this is where the WD-40 comes in very handy. See the small holes inside of the Aluminum housing? Shoot WD-40 directly into the holes, they lead to the screws on the bottom, and are most likely rusted like mine were. (Leaned the hard way, and had to drill out the screw on the right if i recall correctly), Spray Wd-40 on the underside as well.


Step 7: The metal base were the hoses attach to should easily separate, for reference, the spring has less tension then the center spring)



Step 8: You should only have the plastic circle base and the aluminum housing. Push the center pin as far down as it will go (it won't go all the way through, the head is larger than the hole it fits in). EXERCISE CAUTION Then, Lay the aluminum housing upside down and EXERCISE CAUTION gently pry the round plastic housing from the aluminum housing. It will not separate yet refrain from forcing it!!!




Step 9: This is the second most challenging aspect of the whole project. EXERCISE CAUTION this is where the small screwdriver will come in handy. As one can see from observation, there is a spring in the center, and there is a black pin that connects to the green center pin. In between the spring, one should see a chrome U, this is the clip that hold the entire assembly together. The way I separated it is while pulling on the black pin, (holding the aluminum housing down), I gently lifted (refrain from prying and bending the U clip) each side of the clip until the unit separate into two.




Step 10: Cheers, if you on this step you have separated the two. Remove the black pin from the plastic housing, the metal ring, stay attached to the stem.







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Last edited by Assault; 12-29-2014 at 12:03 AM.
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Old 12-28-2014, 11:11 PM
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Step 11: Inspect all of the following parts, then reassemble, there is a washer inside of the rubber seal, leave it in there. The washer and rubber seal combo should be facing downward (the open metal side face down), then the black plastic retainer goes on top, and the metal ring inside of that.






Step 12: Clean aluminum housing, metal base and round plastic piece, as well as the two gaskets. ((leave the electronics alone, scrape off and corrosion if needed). Use a soapy water, and dry thoroughly. Any water reaming will ruin cause the gasket sealant to fail to adhere, and you will have to redo the entire project.

Step 13: Push the green rod in the aluminum housing so that it is protruding as far out as possible. Slip spring over green rod. With the housing upside down resting on the desk. Remove the rubber gasket at the base of the aluminum housing (make sure area is dry) and apply sealant. Press gasket into place and apply a light coating of sealant.


Step 14: This step will require patience and focus. The small screw driver will come in handy again. Hold the circular plastic piece in one hand, align the black pin and the green rod as closely as possible. With your free hand take the screwdriver and push the center of the black pin from what would be the bottom of the servo (see picture). Now carefully join the black pin to the chrome U clip on the green rod. Watch the brass rod protruding holding the metal ring and stopper, it must go into the hole simultaneously. They should lightly click together. Compress the round plastic piece and aluminum housing together. If you find they won't compress, don't force it. Turn the green rod clockwise from the top aluminum housing just enough to close the gap and seal them.


Step 15: Apply sealant to the base of the Servo (as pictured above) then press the gasket into place. Reattach the metal base. Screw down most to where there is at least 1/4 to 1/2 turn left. In and hour or so you will need to finish tightening the screws down.


Step 16: Spread a layer of sealant around where the top and bottom of the plastic round piece.


Step 17: Flip the unit over so it is upright. Fill the two screw holes with sealant.


Step 18: Reattach the center pin in reverse order you removed it. Flip the metal plate over on top of the center pin. You will need to enure the motor and the center rod assembly are aligned properly. Right now the rod assembly should be fully extended. Refer to step two and run the motor until they are synced up properly. One direction will raise the rod assembly the other direction will lower it into place. (refer to step 19 picture as well)


Step 19:
In the picture below there is a rubber/metal piece that appears to be over the red and Orange wires. If it falls out, place it into position on top of the metal clip, that rest over the black arm and slip the rubber cover over and screw it down. You will need to maintain pressure on the rubber plate until you have two screws in. Ensure all screws are snug tight. Tip: you may need to remove the gear with the two green wires going to it. It is okay to do so, it simply reattaches once the rubber plate is screwed down.


Step 20: Reattach the cover. Remember in an hour or so, probably 30-45 by now, finish tightening the screws at the base of the servo. Reattach to car.

Step 21 (optional): Roll one up , put a movie on and grab a beer .

Theory on why plastic servos fail: 1/16 of an inch causes total servo failure (theory))
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Last edited by Assault; 12-29-2014 at 12:03 AM.
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Old 12-28-2014, 11:20 PM
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The cap to the motor fell of! What to do. Remain calm, Inhale, Exhale.





You will want to get the metal rod in the center of the motor, between the metal tabs on the cap. If you are working with the plastic servo motor,tabs go under the blue cap. A small screwdriver will come in hand, or a toothpick, angle the motor and the cap so you are looking down at it, when putting them back together.
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Old 12-29-2014, 06:01 AM
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Location: Bahama/Eno Twp, NC
Posts: 3,258
Nice write up! Glad I don't have to deal with this issue.

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Benz Fleet:
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