Has anyone ever tried to fix/rebuild the climate control servo? - PeachParts Mercedes-Benz Forum

WANT '71 280SEL · #1 11-11-2003, 04:54 PM

Car is the 1979 300SD w116. Mine isn't working now. If I remove it and spray wd-40 in the small holes and put it back in it will work. I did that like 2 months ago, and it worked until recently it wouldn't work intermittently. I know this can be rebuilt because I have seen them for sale but is it something that I could do or is it too sophisticated? Also, how do I check the amplifier that is behind the glovebox?
Thanks
David

Gilly · #2 11-11-2003, 07:57 PM

I've always heard that they seize internally. Never even tried to disassemble one. "Replace it" seems to be the order of the day, but you probably have nothing to lose by taking it apart.

Gilly

Kyle Blackmore · #3 11-11-2003, 08:12 PM

To check the amp , remove the glove box (123's anyway) and then remove the amp. It's a black box with mesh openings about the size of a deck of cards.Open the amp up and check the soldered connections on the circuit board , if they look burnt the amp may be beyond hope. Mine were brown and I resoldered the entire board , it's worked fine since. Fix the servo first then the amp , I believe the servo (if it seizes) will fry the amp. Good luck.

Fisherman · #4 11-12-2003, 02:44 PM

Most of the servos that I have seen failed due to the plastic body cracking. I've got to think that internal corrosion may have something to do with this too. I've got one that is cracked in my pile and would love to give rebuilding it a shot but where does a guy get the aluminum body or just another good plastic body to use in the rebuild process?
I'm guessing that the rebuild shops have them built specially for their use but maybe someone knows of a source?

WANT '71 280SEL · #5 11-12-2003, 04:14 PM

The thing is though, mine isn't cracked. I just don't think it's opening. When it would work I could turn off the car and hear it close. I know it did that when I had defrost on when the car was shut off. You would have to open the hood and stand by it but you could hear it run for about 15-20 seconds. That is why I am wondering if it may just be something simple on the inside that I will notice wrong right away.

WANT '71 280SEL · #6 11-12-2003, 04:16 PM

I think there are 10 wires going into it. Do any of you guys know what color/wire should be getting what voltage; so I could maybe make sure it is getting the proper electricity?
Thanks
David

Fisherman · #7 11-12-2003, 05:11 PM

I don't know if you have ever looked at the troubleshooting doc on the CD for the servo but it has like 2 tests and that's it!
Really lame..

I just looked at all the wires, the vacuum tubing and the brass bars on the top and decided to stop there...

Now you've got me thinking to tear into it since my case is broken anyway and see if I can make heads or tails out of the thing.
I'll let you know what I find, if I can get a chance to get to it.

WANT '71 280SEL · #8 11-12-2003, 05:33 PM

I want to tear mine apart but then I don't have a way to get to school. Chances are, when I get it aprt I will break something rendering it useless. I am thinking of maybe just bypassing the servo for now by just using a pice of pie to connect the hoses together. I just need to figure out which hose goes where.
I want to wait till after I subscribe to Thomaspin's site so I can see what his is alll about with the climate control.
Thanks
David

Gilly · #9 11-12-2003, 06:56 PM

There is (or was) a tool available for easy testing of the servo. It consists of the electrical plug (like the one on the harness that connects to the servo-motor) and 4 wires. 2 of the wires are to power the servo-motor. The leads are long enough to reach a battery, either the car battery or a test battery. The servo-motor evidently runs on less than 12 volts, as there is a resistor to evidently step down the voltage, but I don't know the operating voltage or info on the resistors used. The other 2 wires you connect to an ohm meter to monitor the feedback resistance. Movement in the resistance indicates an operating unit.

Maybe someone has info on the parts needed to make the tool. Maybe I can try fishing up some info myself too.....

Gilly

Lycoming-8 · #10 11-13-2003, 12:59 AM

Located the following site while looking for info on various aspects of our '64 Imperial. Lots of good info in the "servo" section including an internal layout diagram for their servo. Can't rember seeing a circuit diagram but it at least explains some of the internals for this somewhat mysterious part.

imperialclub.com/Repair/Lit/Master/281/index.htm

#11 10-07-2004, 12:33 AM

Quote:

Originally Posted by WANT '71 280SEL

If I remove it and spray wd-40 in the small holes and put it back in it will work.

Where are the holes located that you sprayed the wd-40 down? I am almost tempted to do this, as long as it doesn't require too much disassymbly...

hockeynut · #12 10-07-2004, 08:48 AM

When I bought my '79 300D in August the servo was bypassed. The seller told me she did not want to spend the money so her indy shop suggested the bypass. They just connected the lines straight through under the servo - leaving the servo in place and connected. Problem with that is you have heat all the time and the climate control buttons cause some pretty neat reactions when you press them

I did not want to deal with the heat and also wanted some functionality so I had my indy install a rebuilt - all is well now. The rebuilts seem to run about $350 from most places.

Rusty Cullens · #13 10-07-2004, 09:37 AM

I know that there is a rebuilt servo out there with an aluminum body that won't ever crack. The price on them is roughly a 1/4 of a new plastic one.

WANT '71 280SEL · #14 10-08-2004, 01:30 PM

The holes are rectangular and the perfect size for the "straw" to fit into. It has to be out of the car to do this. They are abouot mid-way up on it. Also, you many want to spray carb cleaner first to clean up the inside if necessary. Or, just put a wanted ad in the parts discussion and see how much you can get one for. Are you sure it's your servo? It could be the push-button unit or the amp on the passenger side under the dash.
Thanks
David

boneheaddoctor · #15 10-08-2004, 01:39 PM

Quote:

Originally Posted by Lycoming-8

Located the following site while looking for info on various aspects of our '64 Imperial. Lots of good info in the "servo" section including an internal layout diagram for their servo. Can't rember seeing a circuit diagram but it at least explains some of the internals for this somewhat mysterious part.

imperialclub.com/Repair/Lit/Master/281/index.htm

That is so cool. I have been looking for something like that since I bought my car.