Author Topic: 55Amp alternator  (Read 767 times)

MarkCan

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55Amp alternator
« on: October 12, 2021, 17:44:11 »
I’m looking for the Bosch 55Amp alternator. I see 74x,
https://www.boschautoparts.com/en/auto/alternators-and-starters/remanufactured-alternators?partID=AL74X
With the new style plug that allows for internal regulator. For some reason I don’t see them listed with the internal regulator.
Would anyone have the part number for the internally regulated Bosch 74x alternator?

WRe

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Re: 55Amp alternator
« Reply #1 on: October 13, 2021, 07:30:47 »
Hi,
that should be the same part number (or Bosch 0986031020) because you can change the brush holder with an internal regulator including brushes (Bosch 1197311090).
...WRe

MarkCan

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Re: 55Amp alternator
« Reply #2 on: October 14, 2021, 01:01:46 »
Hi,
that should be the same part number (or Bosch 0986031020) because you can change the brush holder with an internal regulator including brushes (Bosch 1197311090).
...WRe
Thank you WRe.
I purchased the Bosch alternator from RockAuto this morning. Here is the link;
https://www.rockauto.com/en/partsearch/?mfr=BOSCH&parttype=2412&partnum=AL74X
AutohausAZ has it as well for about the same price.

WRe

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Re: 55Amp alternator
« Reply #3 on: October 14, 2021, 06:44:38 »
Hi,
you probably need the internal regulator too: https://www.rockauto.com/en/parts/bosch,1197311090,voltage+regulator,4884.
But there are a lot of compatible regulators on the market.
...WRe

Tyler S

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Re: 55Amp alternator
« Reply #4 on: October 18, 2021, 15:01:47 »
Please replace the B+ cable from the alternator to the back of the starter with at least an 8ga wire. The factory 10ga is only rated at 30 amps and is not fused in any way. If the 55 amp alternator ever full fields it will start a fire.
1968 (67) 250sl. 4 speed manual. DB180 Silver
1955 220 Cabriolet A. White Grey
2019 E450 Wagon. Majestic Blue
1936 Ford PU Flathead V8. Creme on tan interior.
1989 Volkswagen T3 Westfailia Campmobile. Dove Grey (blue)

mdsalemi

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Re: 55Amp alternator
« Reply #5 on: October 20, 2021, 13:54:37 »
While it definitely isn't as popular a question (we get far more questions than actual executions of the "upgrades") as say, a 5-speed or 6-speed or rear axle ratio conversion, the larger alternator does come up now and then.

Why?

Our cars seem to be able to handle a normal set of driving lights and or fog lights (you know, those bumper mounted ones) with a standard alternator. Some of the newer ones lamped with LED bulbs use a lot less current anyway. Even an "upgraded" radio, that Becker with the separate amp, doesn't seem to present a challenge. If your standard electrical system is up to snuff, it shouldn't have any issue keeping a good battery charged, or serving the electrical needs of a Pagoda.

The usual reason in the automotive world for a larger alternator is for those extremely powerful stereo systems (those with the giant speaker box in the back, massive subwoofers, etc.) and or those banks of extremely powerful lights such as those used in rallys. At night. In the woods. Rarely do we see anyone doing this in a Pagoda. Joe Alexander in his W111 rally car, but not a Pagoda.

So, why would we want a larger alternator? Just because "bigger is better"? Or are people running high capacity electrical devices we don't seem to know about?
Michael Salemi
Davidson, North Carolina (Charlotte Area) USA
1969 280SL (USA-Spec)
Signal Red 568G w/Black Leather (Restored)
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lpeterssen

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Re: 55Amp alternator
« Reply #6 on: October 20, 2021, 19:52:56 »
I agree with prior comment on the real need for a larger alternator.

Frequent battery discharges is the consequence of an aging wiring harness which has lost its insulation quality on those lines which are always energized.

The common approach is to change the alternator for one with larger capacity.  I had the exactly same experience on my first steps into a classic MB.

My car drained the battery frequently, and the culprit at the end was the harness, not the alternator.

That is how I started on this work/hobby of restoring wiring harness. The day I decided to put my hands on and solve finally the problem that no mechanic or electrician wanted to solve. Only minor hot patches were given to my classic MB.

So my advise to you all, is to put your hands on if you have the skills and take out the main wiring harness. It is impossible that is in great shape as on day one.

It has 50 years my friends, is old, cracked and tired.

Yes it is a lot of work, but your car deserves it.

You are at the risk of fire and you do not want to realize it.

This is how a charging loom looks ALWAYS, when I put my hands on them.

See below.

Best regards
leonardo Peterssen

mdsalemi

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Re: 55Amp alternator
« Reply #7 on: October 21, 2021, 14:43:40 »
Frequent battery discharges is the consequence of an aging wiring harness which has lost its insulation quality on those lines which are always energized...
The common approach is to change the alternator for one with larger capacity.  I had the exactly same experience on my first steps into a classic MB.

At long last, an honest man, Leonardo!

From an electrical point of view, adding a higher capacity power source (larger alternator) to compensate for aging wiring (resistance in the conductors) only means MORE CURRENT (amperage) will be sent through wires already compromised. More current is dangerous and can lead to fires, as you point out.

Though the following is a YouTube example (from Canada) it shows what happens when [abnormally] high resistance is in a wired circuit:

https://youtu.be/nPhgQpRFe5A

Note in the example in the video, the circuit breaker (or in the case of a car, a fuse) did NOT trip. Note also that the narrator speaks of an AFCI breaker which would have instantly caught the arcing and shut off power to the circuit. As far as I know, we don't have such things on cars.

Thanks for bringing to our attention the issue of old harnesses!
Michael Salemi
Davidson, North Carolina (Charlotte Area) USA
1969 280SL (USA-Spec)
Signal Red 568G w/Black Leather (Restored)
2019 Ford Flex SEL
2019 Ford Edge SEL

MarkCan

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Re: 55Amp alternator
« Reply #8 on: October 26, 2021, 16:38:20 »
Thank you for your concern guys.
Now, since I’m rebuilding it all, making new harness is just the part of the process.
New internally regulated alternator is now on the engine.
https://youtu.be/FnkiycW0LFA