55 AMP alternator #

[jeffc280sl]

Does anyone know the part number for the heavier duty alternator?

An old post said 002-154-4602-80 was the 55 amp version.  I've found info that says this part is the 35 amp version.  Is AL72X the correct one with internal regulator?

Thanks

Jeff C.
1970 280SL 4-speed

[TheEngineer]

I got a 55A from a wrecking yard. They were used on the sedans. It uses the same regulator as the 55 A. Plug is the same. Straight exchange. Works great. IMHO plug is the important thing. Fan is cast aluminum instead of pressed steel.

'69 280SL,Signal Red,113044-12-007537,tired engineer, West-Seattle,WA

[jeffc280sl]

Thanks Engineer.

I took my 35 amp alternator apart to inspect,clean and repair if possible. Brushes looked fine so I reassembled the unit and reinstalled it.  Performance was about the same as before.  As electric devices (lights, wipers, radio, amp) are turned  on the battery voltage drops.

After starting the car with a fully (trickle) charged battery I read 13.3V at a new battery.  I read the same output at the alternator. This reading drops as electrical items are turned on.

Conclusion 1  This means the wiring between the battery and alternator is good.  I think the voltage regulator is good.

I understand that if all is well the battery voltage should be between 13.6 and 14.6 with the engine running.

Conclusion 2 Alternator output is a little low

With the car running I disconnected the voltage regulator and placed a jumper wire between the DF terminal and the battery output post on the alternator.  There is a small arc and when the jumper was connected it caused a slight drop in engine rpms.  

Conclusion 3 Alternator diodes are ok

Conclusion 4 Replace alternator

I've been doing some research on alternators.  I see where some have installed 55amp alternators with external voltage regulators and other with internal.  There are many Bosch models to choose from.  Some have recommended using a 65amp version indicating it draws 1/4 hp more from the engine than the 55amp.

I'm considering a larger capacity alternator.  

Does anyone know where I can find specs and dimensions on Bosch alternators so that I can make sure whatever I buy fits properly?

Jeff C.
1970 280SL 4-speed

[Naj ✝︎]

Jeff,
With a properly functioning alternator, i get 14.4 volts at battery with engine running.
55a alternetor Part #s:

MB: 008 154 3202
Bosch: 0 120 489 506
Bosch Exchange: 0 986 031 020(This is what I've used on my 280)
Comes without pulley. Has internal regulator.
Needed new plug and ran extra wire to D+ from loom.

Download Attachment: Alt55aIR4.JPG
31.61 KB

naj

65 230SL
68 280SL

[jeffc280sl]

Thank you Naj!  That's what I was looking for.



Jeff C.
1970 280SL 4-speed

[jeffc280sl]

New alternator installed and operating properly.  It's a very easy bolt in place upgrade.  You will need a to add a new connector to terminate the battery and D+ leads on the 55 AMP alternator.  After much searching I was able to pick one up at a local alternator repair shop.  The connector had an AMP logo on it and the receipt called it a Plug Kit-Lucas #46-92800

Jeff C.
1970 280SL 4-speed

[rwmastel]

quote:Originally posted by jeffc280sl

You will need a to add a new connector.....

We will need a what?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[jeffc280sl]

Rodd,

There is a three pin connector on the rear of the alternator.  The existing connector for the 35 amp alternator is not suitable for the 55 amp alternator.  Hence a new connector is required.

Jeff C.
1970 280SL 4-speed

[rwmastel]

OK.  I thought you were writing that "You will need a {word removed?} to add a new connector..."  I thought you left out the name of a tool or part or something.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[J. Huber]

This old thread has suddenly become very relevant...

Last night, a 20 minute errand turned into a 5 hr ordeal that included a nice ride on a flat-bed tow-truck!

I was making my way along, shortly after dark when the car just lost power, sputtered and quit. Immediately thought it had to do with my recent install of points? ... but the car would not crank -- no power whatsoever. My new guess was electrical. I then messed with battery cables, thinking that could be it. Nothing. I crawled under to see that starter wires were in tact, and for good measure gave the starter a couple whacks with a wrench. Nothing. The friend whose house I was heading for knows nothing about cars but he had jumper cables. We jumped it, and the car started as usual. But when the lights were switched on, off it went. Tried again, same deal. I followed him to his house with lights off -- and we trickle charged the battery for a good hour. The battery had a charge -- and I had to get home, so I went for it. Car and lights were fine for about 3 miles, then sputter, a few backfires, and gone. Nothing. Enter AAA and the flat-bed. 

So here we are: does this sound like an alternator issue to you all?
If so, am I correct to think that the 55AMP will work in my 230SL?
Anyone have exact details on what I will need?
And the 60,000 dollar question: is changing an alternator something I could manage myself?
Anyone care to spell it out? I don't see much in the Wiki (yet!)... Thanks

[hauser]

I made the switch to a Bosch 55 amp alternator.  The only difference that I know about is the location of the plugs.  Th Bosch unit plug is 12 o'clock and the MB unit is at six or something to that effect  (according to Gernold).  Bosch builds both units but for "show" it might be best to go MB.  BTW the retail price is about the same( also according to Gernold).  Had I known this I would have gone with the MB alternator.

[J. Huber]

Well, the first thing I want to figure out is what I have in there now... if I can understand the current wiring it may help me comprehend the change-out

The tag says Bosch 0 120 400 512

On the back there are 4 connections:

D-  has a yellowish from main harness and a small ground strap

DF - has a black from main harness

B+ has a yellow from auxillary fuse box and a wire from main and a wire to the starter

#4 I can't make out but it has a red wire and a small condesor looking thing

Does this sound like an original 35 -- and do connections match what they should...

[Naj ✝︎]

Hello James,

If you've got all the wires secured on studs by nuts then that is the original alternator.
Later alternators had the big wire B+ on a stud/nut and the other wires were on a 3 pin plug.
#4 shud read D+.
You will find that besides the B+, the other three wires go to the voltage regulator.
I would go for the 55 amp alternator with internal regulator (which will be electronic).
You will need a new plug for it, which has 3 wires, 2 bigger terminals take the 2 B+ wires and the 3rd smaller terminal will take the D+ wire which operates your alternator charge light on the dash.
The Bosch exchange alternators have different part #s to the European system but I'm sure Al has posted it before.

Hope this helps

naj

[bpossel]

James,

What I would do before replacing my alternator, is to ensure that my alternator was defective.  Your original issue could be: wiring (short); defective battery cable(s); defective alternator; defective voltage regulator; and/or defective battery...

A "cheap" initial check could be performed at one of your local auto parts store if the car is driveable and if you have a local store that you trust.  Here in Memphis, AutoZones are pretty good, as long as you get the right person!  They can use one of the stores testers and test the charging output of your alternator.  They can also put your battery on a bench tester and test without any cost to you.

Sometimes pre testing of these components will yield a different conclusion and save you some $.

Another suggestion..  did you do any recent work on your car before your problem started?  Did you change, adjust anything?  Sometimes a simple change, adjustment in these cars can cause an issue...  If yes, try reversing what you did...  relook at everything you touched and see if this could cause your issue... 

Good Luck!
Bob

[graphic66]

The very first test to make is to make sure the charging bulb in the dash is working. Turn on the ignition to the run position without starting the car. If the bulb is on it is working, if not you need to get the bulb working. The current through the bulb excites the alternator and gets it charging. Sometimes it is just a bad connection at the bulb or the bulb is blown. Without this bulb working your alternator wont charge. I have a 66' 230SL with AC, 100/55 watt H4 headlamps {the best upgrade ever for only $75.00, better than a 55 amp alternator, I think] and The 35 amp alternator supplies plenty of power. The 55 amp may be a nice upgrade but in my opinion really isn't necessary unless you have added more draw to the system like a giant stereo or some huge driving lamps.

[bpossel]

Hi Graphic66,

If you dont mind, I am going to add your test to the manual.  Thanks for this info!  I know this was a test that you sent me awhile back, so want to add to the manual for future...  Thanks!  Bob

[graphic66]

I would be honored! I found out this test on my Mercedes U900 406. It wasn't charging out in the woods. Pulled the alternator right there on the trail during a break, tested the diodes and brushes. Everything was great. Then I did the first step of diagnostics last, got the manual out of my toolbox. Lo and behold it said to first check if the alternator light was working. Pulled out the instrument panel and wiggled the bulb and it lit right up. I later replaced the bulb and cleaned the contacts and put some silicone dielectric grease on them. Also, if you do have your alternator apart, which by the way is very easy, remember to grease the back bearing while your in there. The only special tool needed is some string to hold the brushes out as you slide the alternator together.

[J. Huber]

This is great input. Thank you all.

Here's what we have so far. My alternator is obviously the original. Records show it was "rebuilt" in 2002 because output was 15... It has worked adequately since then (roughly 15,000 miles). The battery is one year old. The voltage regulator is a replacement I put in in 2006. Mainly because it seemed easy!
 
The wiring at the back is a little messy although everything seems connected to the alternator nice and tight. I seem some exposed stranded wiring that comes from the starter region to the B+ and from the main harness to the B+. should this be bare? Some flaky stuff falls of this wire...

The 3 voltage regulator wires go into the main harness by the shock tower -- and seem to emerge again near the alternator. Yellow to D- Black to DF and Red to the top connector. These would be the 3 that get a new connector if I get a new alt. Is that correct?

As for recent tinkering. Yes. I just had my air filter cannister out as I detailed and touched up that area -- I painted both the cannister and the cannister area. I also cleaned up (simple green to get off overspray) the main wiring harness up to where it emerges to alternator. So I was clearly in the vicinity! Had I had immediate trouble, I would have suspected this -- but car ran fine for a week. HOWEVER, this just dawned on me -- the fateful night was the first time I drove at night.....

Short of taking car to Autozone to test alternator (which I can do tomorrow) -- how should I proceed to re-check wiring???

Thanks agian -- and I appreciate the patience -- most of you know I need spoonfeeding (just once)...

[J. Huber]

UPDATE: Well good news and bad... the good is I have solved the problem. The bad is I am an idiot (this hasn't changed).

I decided to clean up the wiring and go from there. I made my way backwards from the alternator to the voltage regulator. Well, one of the spade plugs on the VR was disconnected! [This was the one that controlled the red light.] That probably did happen with my prior wiping of wires, etc. The connector slid back on very easily (and hence off) so I closed it a bit -- now its on there tight...

This was clearly the problem. I had the battery charged and the alternator tested. And the Voltage Regulator is plugged in! Everything is working now as it should. Phew.

As frustrating as this experience was -- some good lessons came out of it. Besides learning that to change out the original early alternator, I will need to add the three wire plug connector, and if I don't upgrade to 55, the new 35AMP alternator will be the Bosch AL64X. The other lessons are:

1. Always check and recheck wiring before assuming a component is shot. Especially if you have been working near the wires.
2. Understand each of the parts of a system. I didn't realize how critical the Voltage Regulator was to making the alternator work.
3. Always have a light source available. I was in pitch black when my problem occurred. If I could see, I may have found the loose connection.
4. Join AAA. Upgrade so you can request a flat-bed. Just in case... The ordeal sucked but didn't cost me anything...

Thanks guys.

[graphic66]

You can pretty much test your alternator output without any tools. Turn on your headlights with the car not running. Start the car, headlights should be noticeably brighter. It helps if you leave the headlights on for a few minutes before starting the car. It also helps to aim the headlights on something you can see while starting, like the garage door. If you have a DC voltage meter just hook it up to your battery and check it not running the running. You should see it go from about 11.5-12.5 Volts not running to about 13.5 to 14.5 volts running. And don't forget to check that pesky alternator light in the dash.

[al_lieffring]

On the back there are 4 connections:

D-  has a yellowish from main harness and a small ground strap

DF - has a black from main harness

B+ has a yellow from auxillary fuse box and a wire from main and a wire to the starter

#4 (D+) I can't make out but it has a red wire and a small condesor looking thing

Does this sound like an original 35 -- and do connections match what they should...

Glad to hear you found the problem at the voltage regulator.
One more small thing to do before you consider this job done.
The lead to the filter condensor should be moved from the D+ terminal to the B+ where the heavy gage red wires and the lead to the aux. fuse box for the radio are attached.
I don't think this should affect the charging, but it belongs on the other terminal to filter noise out of the power to the radio.

 

[66andBlue]

UPDATE:... the good is I have solved the problem.... The ordeal sucked but didn't cost me anything...

James,
now that you saved a bundle I think you should invest it in a RT ticket to Columbus and attend the PUB. The lessons there might even save you more in the future 
Hope to see you there!

[J. Huber]

Well, Alfred. We think alike. I was just checking out airfares! Unfortunately, its not merely a matter of money. But thanks for the encouragement!

And thanks Al. Sounds good -- I'll plan on moving it. So the "4th" terminal I have is D+? I can't quite make out the marking.

[al_lieffring]

Yes, the regulator wires at the alternator are marked D+, D- and DF these corresponds to the markings on the voltage regulator that these three wires lead to.