Hey guys,


So I've read the big thread on the alternator upgrade, but I swear I could not find an answer to this question. I bought the AL129X alternator to install in my 1984 MB 300D. I'm installing a stereo so I need the extra juice. Any way, I'm going to be upgrading the grounds while I'm in there so I have a bunch of thick gauge wiring ready to go. Anyway, I know the smaller, blue wire is the remote, which I can just splice in to the existing one and be good on that. However, there's the issue of the power wires.

I know most reading on wiring upgrade only mentions the wire going from the alternator to the battery. However, I thought I saw mention of a second power wire going to the starter from the alternator. Is that correct? And is that wire necessary to upgrade?

Like I said, I read the thread, and I even remember one time reading a thread where someone asked this exact question, but now I can't find it. Thanks for any help guys!

Ok guys, so I looked through the thread and I found mention of a couple of different methods. One person mentioned upgrading the wiring between the alternator and the little power distribution block on the fender well.

The other method was doing the wiring directly. I think I like the method of upgrading the wiring between the block and alternator. On the other hand, I'm a bit confused which post goes to which. This is the back of the alternator I own.

http://i24.ebayimg.com/04/i/001/01/d5/bef2_35.JPG

I was under the impression the smaller post was for the remote wires, and the larger one was for the power leads. Is this correct?

I don't know what you mean by remote...

the smaller wire is the voltage sense wire. it powers the field in the alternator to get it to produce current, then it tells the voltage regulator how much voltage to put out, it also lights the bulb in the dash when the alt is putting out less voltage than the battery has...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

the large wire (s) feed the battery, and the starter.
so in addition to the upgrading the wire from the alt to the terminal block, you need to upgrade the wire from the starter to the battery.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Ahhh, I see now. I mistook that wire for the remote lead for electrical accessories.
Gotcha. So if I understand correctly, I'd need to run 2 thicker wires from the terminal block, to the larger post on the alternator, and then a thicker cable from the battery + terminal to the starter? Now, being that I'm doing this for an audio application, is the terminal block going to create like a bottle neck area or should that be okay? I know generally when upgrading the wiring for car stereo, the norm is to run thicker wire directly from the alt to the battery for maximum current flow.

Hmmm. I don't know.
it all depends on the current abilities of the block... on my 87, I took the harness from a 300E with a 135amp alt, and upgraded...
using the al129, in a 123, I'd think the terminal block could handle the current, as it handles the STARTER's draw... but I may not be looking at it correctly. I have not upgraded a 123 yet. I agree, it's the battery that needs the current capabilities of the alt upgraded, the starter's draw should be sized correctly FROM the battery, but the alt wire going to the starter needs to be large enough to handle the current ...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I think I'm starting to see now. Thanks for all of the information so far. It's been really helpful. Let me ask you, from what you know, would there be a major issue with just running a large gauge wire from the alternator to the battery, and either another large gauge wire from the alt to the starter, or from the battery to the starter? The idea being to bypass the terminal block? I was doing some google searching and found this thread...

stan's 1980 300TD

It looks like that guy just did the direct wiring and it didn't cause him any issues. I'm just trying to figure out of the terminal block interfaces with any other electronics or anything. Thanks again for your help so far.

I left the stock dist block-> starter wiring in place and made 2 new cables:

2ga from the AL129X-> Battery

2ga from the AL129X Housing -> Chassis

I left the stock Battery->dist block in place

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the terminal block doesn't have anything to do with the electronics afaik, it's just a mounting point for the alt wiring to the starter. power goes from the starter back to the battery, with the stock wire, so if you powered the battery directly with the new alt, and left the starter wire, and the dist block out of the loop... all the electronics should be unaffected. however, the block needs to stay, as the purple wire from the glow plug relay gets it's signal from there to know when the starter has been energized...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

The cables to the battery are all wrapped tight. Did you pull the OE cable and fish a new one through, or just zip tie or affix the new cable some other way?

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