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1978 450SL (North American 107 w/Euro Modifications)
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53 Posts
Discussion Starter #1
How do I figure out if I need just an Alternator or an Alterator & Generator. I know I need one or both but I know very little about mechanical workings. Don't laugh but I don't have a clue.

I have a 1978 450SL,
 

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Registered
1984 500SL 000760
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509 Posts
you need an alternator if your battery keeps going dead. Generators are not used on modern cars, they are called Alternators.
 

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1986 560 SL
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7,358 Posts
You need an Alternator. Just look up your year and model in any parts list to get the correct device.
An alternator is a device that generates AC power vs. a generator that generates DC power. An alternator works better at idle speeds than a generator.
To further confuse things the AC power is then converted to DC power for storage in the battery.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,362 Posts
Or maybe all you need is the voltage regulator which is attached to the alternator on your year.
 

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Registered
1978 450SL (North American 107 w/Euro Modifications)
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53 Posts
Discussion Starter #6
Thanks Guys & can I do it myself?

The battery is brand new so I'll have the alternator checked and the & the voltage regualtor is this something I can do I changed out alternators in my american cars when I was younger but I'll have to look up where it even is on this car... I've always had it serviced until recent changes which means I'll probably have to do it myself... I don't have to pull the engine or anything do I?
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,362 Posts
Nuts and bolts. It is just that they metric. You can do it. The procedure is here.
Model 107
 

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Premium Member
1975 450SL
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2,440 Posts
Greg,

What exactly are your symptoms? If your battery runs low slowly, you might have a drain, such as a light being on,or a device failing. If it runs low quickly, you might want to have your charging system checked out before you start spending money, in order to spend only what you need to.

Most auto parts stores will check out your system for free. This basically checks to make sure that you'r charging your battery, but European cars have a slightly different charging system; it's a little more 'modular'. The brush unit is a replacable module since it is a "wear item".

There is one difference that comes into play that is a bit of a complicated, though. There is a wire from the ignition switch that provides 12 volts to the alternator, if this wire loses power, then you will be 'running off the battery' to run the car. This is one of the symptoms of the switch part of the ignition switch assembly going out on you.

The ignition switch assembly is in 3 parts, the lock core, the steering wheel lock assembly, and the electrical switch. Each are individually replacable with varying degrees of difficulty, with the switch part not being really bad.

The alternator itself, as mentioned above, is not difficult, about the same as on a small-block Chevy. Just Metric nuts & bolts (an excuse to buy more tools !!!!!:thumbsup:)

Also, if you do need an alternator, you might want to check into having your unit rebuilt. That can come in a major chunk of money less than new or remanufactured. Check in the Yellow Pages under Auto Electrical. I had one rebuilt in about 6 hours for $80.00, but I didn't need to replace the brush module as I had dome it a few moths earlier.

I know that you probably weren't expecting someone to go into so much detail on you, so please forgive me, I have a tendency to sort of "core dump" every once and a while.:eek:

Good luck, and keep us informed of how this turns out.
Scott
 

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Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,534 Posts
Alternator voltage regulator

The "brush module" is part of the regulator unit at the back of the alternator. Normally only the brushes or the bearings wear out- not the winding so it's no big deal. An auto electrican can quickly tell you if the alternator is working. As previous posters have said there may be other issues causing your problem.
 

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Registered
1978 280slc
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3,203 Posts
To test the alternator, you check the battery voltage with the car off, it should be around 12.5V or so. Fire up the car and measure the voltage at the battery with a multimeter it should be between 13.5V and 14.5V. If you don't have a volt/multimeter go buy one for 20$, an indespensable tool. If your voltage is less than 13.5v I'd say your alternator is on the way out. What I've found is that one brush in the alternator assemble wears down faster than the other and causes a low voltage condition to the battery. If you alternator voltage goes below 12.5V you will be running off of the battery. In an emergency you can put the car into lower gear to raise the rpms. Higher rpms cause higher voltage output from even a dying alternator. If the voltage regulator is still good you can replace only the brushes but you have to solder them in I believe.
 

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Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,534 Posts
DIY removal is not hard- just a few bolts. You need to be a bit careful with them though, use a good penetrant first. Take the alternator and it's mounting bracket off together. Loosen the adjusting bolt first to free up the belt. Removal is in the manual. If you don't have one there's a freebie in the sticky section of this site.
 

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Registered
1978 450SL (North American 107 w/Euro Modifications)
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53 Posts
Discussion Starter #12
It's the Voltage Regualtor

First off thanks for all your assistance all you guys ROCK... so THANKS AGAIN...

BTW the Pictures really helped..

OK I just got back from getting my Alternator Check & the Tech said 99.99% its the Alternators Voltage Regulator, it was generating zero volts...

SO next question is where can I order one of these, I shopped online & didn't find any Bosch 1 197 311 028 EL 14V 4C...

Once I find one, I'm sure I can swap it out it looks pretty simple...

Any sources, links anyone

Thanks Guys
Greg
 

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Registered
1978 450SL--117K
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1,374 Posts
I replaced mine with a higher output Bosch alternator. I think the stock unit is under powered. Believe it or not, I got it out of a warehouse in NE Minneapolis. They have a huge pile of them in there--all new. about $100.00, IIRC.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Why replace the alternator when all that is need is a voltage regulator?

I'll see what I can find.
 

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Registered
1978 450SL (North American 107 w/Euro Modifications)
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53 Posts
Discussion Starter #16
Thanks

thanks rowdie & all part on order, I appreciate all the help
 

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1978 450SL--117K
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1,374 Posts
Why replace the alternator when all that is need is a voltage regulator?

I'll see what I can find.
because the original is only a 55 Amp and the other one is an 85 Amp. Maybe it's my Minnesota bias, but I think bigger alternators are better since they have enough output to allow for all of the electrical to be in use and still charge the battery. At 55 Amps, you can have a problem even though everything is up to snuff. I am thinking in terms of headlights on, heater/AC on and stereo going. In stop and go traffic, the 55 Amp is likely to have a problem. This would be especially true if the headlights are upgraded.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,362 Posts
I'll give you that but it wasn't the question. 55 amp. will handle the standard electrical system. Nothing wrong with upgrading for us but the OP appears to have limited knowledge and ability. This is not an insult to him and hope it is not taken that way.
 

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1978 450SL--117K
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1,374 Posts
I'll give you that but it wasn't the question. 55 amp. will handle the standard electrical system. Nothing wrong with upgrading for us but the OP appears to have limited knowledge and ability. This is not an insult to him and hope it is not taken that way.
Sure it was--you asked me why replace it and I told you why I did it. When the one in the 560 goes, someday, I will replace that one with an 85 Amp too. Over the years I have just come to the conclusion that in the case of alternators bigger is better. I still have shops around here that will rebuild any alternator or starter. But in the case of what I think is a marginal amperage, I will replace rather than rebuild it. Neither of these cars will be driven in winter weather, as a general rule of thumb. But there are times here when the weather just hits you and it's nice to have the power to run everything and not worry about it. If these cars had a voltage meter in the dash (can't figure out why they didn't) I might not worry about it so much. But at my age, when it's raining and dark out, I need all the light I can get to see the lines in the road. I upgraded the headlights and whatnot on both of them. Those lights suck more juice than the originals did and if I went to Xenon like ScottinSoCal did, I would need more, possibly.
 
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