Author Topic: Horn interior  (Read 6372 times)

gwuisman

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Horn interior
« on: October 10, 2004, 17:21:09 »
I planned to clean the outerparts of my horns. By doing so I discovered that there was rust under the protecting tecktyl. That made me curious about the rust in the interior. And indeed there was rust inside the first horn. This was caused by leaking very thin paper gaskets one cannot get original anymore. After I putted the parts together it was difficult to get the right sound again. A mechanic did the finetuning. I could not inspect the inside of the second horn as I did not succeeded in unscrewing the outer parts. For those who are interested in the secrets of the horn I made some pics.

Gerard Wuisman
1970 280sl

Download Attachment: horn front.jpg
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Download Attachment: horn back.jpg
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Download Attachment: horn interior parts.jpg
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Download Attachment: horn electric circuit.jpg
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Cees Klumper

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Re: Horn interior
« Reply #1 on: October 10, 2004, 22:49:22 »
There is a counterlocking adjustment screw behind the round "Bosch" type-plate that can be turned in small increments to make the horn sound optimally (or make it sound at all: if not properly adjusted, all you will hear is a clicking sound). This is from memory, three years ago, when I fixed the one original horn that is still on my car. The other one was replaced by a previous owner. I don't think these horns are available anymore.

Cees Klumper in Amsterdam
'69 white 280 SL automatic
Cees Klumper
1969 Mercedes 280 SL automatic white

hauser

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Re: Horn interior
« Reply #2 on: October 10, 2004, 22:55:32 »
Someone is selling reproduction horns on ebay.  These horns have chrome faces and a center logo.

1969 280sl 5 spd        1999 ML320          Gainesville,Fl.
1969 Euro 280sl 5 spd
Restored by SLTech
Gainesville, Fl.
http://flickr.com/photos/32962977@N03/show/

66andBlue

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Re: Horn interior
« Reply #3 on: September 21, 2007, 23:50:56 »
After cleaning, painting and replacing the paper (fiber) gaskets I mounted the horns again and when I tried to test them -- no sound but  fuse #2 blew![:0]
Checking with an Ohm meter revealed that one horn had a short from the terminals to the center bolt but not the other although I thought that I had assembled them identically.  Comparing the sequence of the inner parts indicated that the rubber washer shown in gwuisman parts picture was in the wrong place in the defective horn.
So to save others some time who might want to refurbish those horns here are some details of the assembly.

The horn can be separated into 2 parts by removing the 8 screws on the periphery, the outer part with the tuning screw and the sound disc and the inner part containing the electromagnet.
Separating the cover (with slits) from the dividing plate allows acces to the sound disc.


The sound disc is held inplace by a hex nut and 2 washers. Behind the disc is a brass ring with an off-center alignment pin. This ring is separated from the dividing plate by a rubber washer and an insulating fiber disc.
-- On the horn with the short I had switched the rubber washer and the insulator - ouch! --


On the other side of the dividing plate is another fiber insulator, followed by a spacer collar that has a slot which locks the wings of center bolt (that acts as a tuning screw) in place.  A coned washer separates the anchor from the collar.  All these parts have an off-center hole for the alignment pin. 
So, assembly is pretty easy since all the parts fit together like a jigsaw puzzle - as long as the sequence is correct!


Alfred
1966 blue 230SL automatic
« Last Edit: November 14, 2008, 18:54:32 by vanesp »
Alfred
1964 230SL manual 4-speed 568H signal red
1966 230SL automatic 334G light blue (sold)
1968 280SL automatic (now 904G midnight blue)