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  #1  
Old 08-01-2002, 02:23 PM
Gympie
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'76 280S - Cut the condensor wire?

Understand the condensor in this model of car is the cause of the blue coating on the points. According to some service bulletin, it is suggested to cut the wire to the condensor in the distributor. Any skinny on this?

Thanks,
Gympie

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  #2  
Old 08-01-2002, 04:30 PM
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Correct.

It is on the CD. The capacitor was installed there for suppression of interference and is blamed for the blue coating. The fix is, "Remove control line with capacitor and replace with shielded control line."
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #3  
Old 08-01-2002, 08:36 PM
Gympie
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Thanks Chuck.

My hardcover service manual only states:

The blue layer (tungsten oxide) is formed by the arch occurring during the closing stage and the resulting burning of contact material. This arch is above all caused by the discharge of the anti-interference capacitor in the ignition distributor.

A large closing angle (small contact spacing) favors the intensity of the arch and thereby the formation of a layer.

I guess I had better get a CD as I'm finding much of the information in my manual outdated or missing. It was printed in 1994. Oh, BTW what is shielded control line? And, what replaces the female connector in the switchgear? Does it say?

Thanks,
Gympie

Last edited by Gympie; 08-02-2002 at 12:40 AM.
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  #4  
Old 08-01-2002, 09:18 PM
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I would suggest doing some more research before you cut the wire from the points to the condensor... ( capacitor )... The blue coating is not produced by that condensor.. it is caused by the tremendous electrical forces caused by the electrical spark jumping across the opening of the points... a natural condition which allows the magnetic field in the coil to collapse and generate 40k plus of volts... usually radio suppression capacitors are placed outside the distributor... if you take out this item you will have greatly increased wear on the points... an effect the same as an electric discharge machining creates... the movement of material from one side of the points to the other... that capicitor is designed to cut off the spark to minimize that material transfer... so it needs to be working,, and of the proper Ohms...If you decrease the gap in the setting of the points you may reach a condition in which the coil does not have time between spark plug firings to completely recharge...not enough "saturation" time.... This is just my guess.... ... Greg

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  #5  
Old 08-01-2002, 09:29 PM
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The documentation was very clear that (a) the condensor was there to suppress interference and (b)that it was the cause of the blue film, and (c) the factory was unhappy because techs were replacing the control units unnecessarily. On my car a condensor is still in there with the wire cut.

Sounds like the same thing your manual says.

The green wire from the CD unit is connected to the wire coming off the points. It looks like a replacement wire, not a hack.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #6  
Old 08-01-2002, 10:10 PM
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Location: Florida / N.H.
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The early Bosch TCI ignitions were point switched transistorized switchgear...
So, the load of the coil is not on the points, but on the transistor.
The points simply feed low current to the base of the switching
transistor circuit.
The problem they were having was the condensor was causing
blueing and failure of the points.
The remedy [ per Benz] was to eliminate the condensor from the circuit as its purpose was to just to clean up the wave form to
the transistor base feed...[ interference ] , They were more troublesome then the benefit of the wave shaping.
After it is eliminated , the point surface will last very long cuz of the low load of the base current to the switching transistor that the points switch/feed... [independent from coil load]

These points were later eliminated in favor of Hall Effect system
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  #7  
Old 08-02-2002, 01:03 AM
Gympie
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Thanks all. Think I’ll give it a cut. The points don’t last long and do develop a blue coating. What is the procedure; give it a snip between the condenser (capacitor) and the breakers?

Gympie
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  #8  
Old 08-02-2002, 08:03 AM
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Mine was cut right at the condensor, and the wire removed.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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