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  #1  
Old 08-04-2003, 01:52 PM
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Join Date: Feb 2001
Location: Midwest, USA
Posts: 171
alternator swap/ positive terminal/black box

I just received my gorgeous new Bosch alternator from Mercedes shop. It is identical to mine, came with a new Bosch internal voltage regulator, but did not come with the little black box with the wire going to the "+" terminal and bolted to the rear of the alternator.

I took mine off to look at it and I assume to swap it over to the new alternator. It's rectangular and says nothing at all on it. The wiring terminal does say, "amp" and "180984".

First of all, what is this thing? Secondly, mine is cracked on the outer shell, is this a problem? Thirdly, why do you suppose the new alternator doesn't come with this? I think I'd like to get a new one before I install this.

Thanks!
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  #2  
Old 08-04-2003, 04:12 PM
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Join Date: Jul 2001
Location: Old Lyme, Connecticut
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'79 Super Turtle,

It is possible your car came with an external voltage regulator. As I recall the connection from the alternator to the electrical system is a small black plug and there is a loose wire that gets connected to the frame or body of the alternator with a screw. I have not done this job in a while but I believe that wire is green and comes from the same set of leads that has the black plug. To get a definitive answer I would call Phil at the Partsshop. Click on the tab at the top of the page and get the phone number. Phil is a great guy and will definitely know how to get you an answer. Good luck, Jim
__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #3  
Old 08-04-2003, 07:07 PM
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Join Date: Feb 2001
Location: Midwest, USA
Posts: 171
Thanks Jim for the response. Phil and I are buddies. He is wonderful! I was hoping not to bug him about it. My two '79 300SD's both have alternators with the internal regulators. I have the black wiring plug with the three connections, and the alternator I am replacing is identical to the alternator I received in the mail. What I'm curious about is the small rectangular box that plugs into the "+" terminal and is screwed on the back of the alternator. Both of my cars have this on their original alternators, but the replacement did not come with it. I am going to switch it over, but was hoping to find out what it was for???

It's a curious thing.
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  #4  
Old 08-05-2003, 12:54 AM
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Could that be a static supressor? Seems I remember that black box but its been a while.
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1985 Euro 300TD 5 spd 220K
1985 Euro 240D 5 spd 130K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
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  #5  
Old 08-05-2003, 09:16 PM
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Hey Stevo, I was thinking it was something like that. I was just told by Bill at Parts shop that it is a condenser.

Does anyone know how to test it to see if it is still "condensing".

What does a condenser do?

Thanks for the replies so far.
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  #6  
Old 08-06-2003, 12:10 AM
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Join Date: Jan 2003
Location: kansas
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the condensor on the back of the alternator is used to filter out radio frequency (rf). rf is generated anytime there is a spark, it is a very small signal but large enough to render your radio usless. a quick test is to start the car, turn you radio on a.m. and listen, if you can hear it without alot of noise overrunning the station it is ok. note, most radios including our beckers incorporate "filter" circuitry in them. thus, the condensor keeps your noise out of the guys radio next to you at a stop light.
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  #7  
Old 08-06-2003, 12:58 AM
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'79 Super Turtle,

A condenser is another term for a capacitor. Capacitors are made up of many layers of conducting material separated by insulating material, with every other layer of conducting material shorted electrically. One set of these layers is one polarity and the other set is the opposite. This arrangement allows you to store more electrons in the negative set of conductors than would be feasible at a given voltage if the same surface area or volume was spread out in the open. The term "condenser" comes from the ability of this geometry to store electrical charges in a smaller volume.

Condensors or capacitors do not conduct direct current, but they do conduct alternating current. In the application noted the intent is to take the alternating current component, due to the interruptions in current flow resulting from the brushes and the commutator, and run it to ground while preserving the DC output to go to the battery. If the insulation system fails in the condenser you would know it because the system would not charge your battery correctly either and it would likely burn out the little black box, taking out of the electrical circuit. If the condenser is disconnected by this or another means you will detect a buzzing noise on the radio that runs with the engine speed - higher engine speed gives a higher frequency buzzing.

Hope this helps, Jim

(edit for clarity)
__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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  #8  
Old 08-06-2003, 10:27 AM
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Join Date: Feb 2001
Location: Midwest, USA
Posts: 171
Perfect! Thanks to all, and to you Jim, excellent description.

I guess I'd better hook up the radio!
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