Upgrade to 55 A alternator

[Roman Kishi]

I did my home work and searched the site but I couldn't find the answers. This maybe a good subject for the manual.

I have few questions for the electrical Gurus about upgrading into 55 A alternator:

-Does it have an internal voltage regulator? and if so do I need to bypass the old one(keep it outside the circuit just for the originality)

- The electrical plug of the 55A  looks different than the 35A, do I need a new one? what's the part number? any other wiring modification I have to do.

- Do I need a new pulley?

Thanks for the help, I love this site

[awolff280sl]

Hi rkishi,
I recently made the 55amp upgrade. I went with a Bosch AL72X which is externally regulated and kept my original regulator. I think that the AL74X is the internally regulated one and does require a plug adapter for our cars. JeffC280SL can give you some info on this.
The pulley was a problem for me because I bought a new alternator that did not come with a pulley. My original 35A was mounted up high with the original York A/C system, and I remounted it in the low position to install a rotary compressor up high. The original pulley on the 35A was too wide for the standard belt because it was designed for the A/C system. I eventually pieced together a pulley/fan assembly from a used alternator off of a MB sedan. The important points that I found out when getting a used pulley that worked were:
1: appropriate width for the belt, & no deformities
2: fan cannot scrape alternator housing
3: proper assembly of the washers, woodruff keys, bolts
Hope this helps.

[mdsalemi]

I'll have to check on this.

Seems to me I've seen the full instructions on this, either in the MBCA's Technical Reprint, or something similar.  I'll take a look in the next few days and post what I find.

[Naj ✝︎]

Roman,

Have a look at these posts:

http://index.php?topic=5026

http://index.php?topic=3477

If you use the Alternator with internal regulator, the two bigger wires from the B+ terminal connect to the two big spade terminals and the patch from the blue wire at the regulator connects to the smaller spade terminal in the plug.



Alternator Plug



naj

[114015]

Hi Rkishi,

As you already read from the others, yes, this is possible.
I chose the more complicated and (to my eyes more) elegant way.

I got an original Bosch 0120 400 532 alternator (230 late, 250 and (I believe) early 280SL) professionally converted from 35 to 55 amps. Stator and armature were replaced with larger equipment & the whole assembly overhauled.
It now looks completely original with the exception that the stator (and with that the length of the complete housing) is about 1/4 of an inch longer than before. However, this does not affect the mounting points or the pulley of the original alternator and is barely visible!

Since our cars always had/have the external voltage regulator, which is mounted on the inner right fender and that one is capable to do right with a 55 amps alternator as well, no other conversions are necessary.

I chose this way because I absolutely wanted to keep the classic look of the original alternator at all costs. I hate to have a look of a "later seventies style" alternator, especially regarding its beautiful casted original pulley/fan assembly and furthermore wanted to keep the original integrity of the wiring harness' connecting ends to the alternator. Therefore, this weird plug assembly or any other later style alternator was (and is) a "no go" for me.

The next one for conversion (0120 400 504, the original early 230 style alternator) will get an 65 amps upgrade ... hopefully.

Best,

[thelews]

What is the advantage of the higher amp output, assuming one is not running a multitude of add ons off the cigar lighter?

[114015]

John,

14 V x 35 amps = 490 W total is not much nowadays.
If you are putting better head-& taillight bulbs in you will already need about 50 W more. You're running short especially if you need more of the Watts-eating stuff like wiper, blower motor, etc.
The most important reason is to maintain a better Stereo. That's for what I am going to use it.
http://index.php?topic=8344

Best,

Achim

[jeffc280sl]

I have the 55 AMP alternator and did the upgrade in order to provide power to a stereo amplifier and eventual replacement of the mechanical fan with an electric one.

[TR]

I find that my new 160 amp alternator does just fine when it comes to powering the built-in seat heaters, seat coolers and back massagers from Webasto.  It doesn't have any trouble powering the in-line heater for the windscreen washer fluid either.  I could go on (and on), but out of a desire to maintain peace won't...

[hauser]

I had mine upgraded to the 55 amp Bosch unit.  Pretty much the same as the 55 MB alt with the exception of the plug location.

[mdsalemi]

I thought there were step by step instructions in the Vintage Reprint (MBCA) from a few years ago.  Took me a long time to find my copy but alas it wasn't there.

However, in the Mercedes Collector there was an article about such upgrades more general to all older MB's rather than specific W113, and I think it was Frank King who stated that as long as you stay within the same "group number" of alternators, you are OK.

Maybe that can be elaborated on further.

[Roman Kishi]

Hi Naj, or anyone:

Thanks for your help. I got this picture from one of your posts. I can't find the right Pulley, any idea what car model/ year it came from? Bosch parts # in US are not always the same as EU.

http://www.sl113.org/forums/uploaded/naj/2006410165012_Alt55aIR4.JPG

[Naj ✝︎]

quote:Originally posted by rkishi

Hi Naj, or anyone:

Thanks for your help. I got this picture from one of your posts. I can't find the right Pulley, any idea what car model/ year it came from? Bosch parts # in US are not always the same as EU.

http://www.sl113.org/forums/uploaded/naj/2006410165012_Alt55aIR4.JPG

MB #s (please double check with your dealer!!!)

000 155 8418 fan
001 155 3415 pulley

naj

[KUMARB]

I am also upgrading to a 55Amp alternator in my 280SL. The old one was 35Amp, Bosch AL 64x. The new 55Amp alternator Bosch AL 72x is identical to 35Amp with similar connection posts and external voltage regulator.

I am also changing the A/C York compressor to a Sanden 508 compressor with an auxiliary cooling fan. With all the electrical loads, like lights, windshield wipers, heater blowers, air-conditioning, radio with power antenna, etc., 35Amp appears to be slightly overwhelmed. Hence, the need for upgrade. Later MB SL models, like 45OSL or 500SL, have 70-80Amp alternators.

Good luck with your upgrade project!