For those who have done the AL129X alternator swap - PeachParts Mercedes-Benz Forum

lowriderdog37 · #1 07-22-2008, 12:22 AM

I am picking up my alternator tomorrow. For those of you who have done this swap, what have you done about the issue with the AC hose?

I saw in the installation writeup from 81Wagon that there was possibly an issue with the AC hose clearance. I am not as worried about installation, as that can usually be worked around, but the hose rubbing on the back of the alternator after installation. Any thoughts?

"Alternator" 115 Amp Bosch AL129X works in 123s!

300SD81 · #2 07-22-2008, 12:26 AM

What car are you installing it in? In a W126, there is absolutely nothing in the way, drops in as easily as the stock alternator comes out, not sure about the W123.

81Wagon · #3 07-22-2008, 12:43 AM

The back of the alternator can be rotated (I think in 90 degree increments; there should be four equally spaced screws but it's been a long time since I've looked at mine!) so I think you should be able to get the various connectors into an accessible position. There shouldn't be any physical contact between the alternator and the AC line. Hopefully someone can confirm this though.

Enjoy your new alternator

.

BoomInTheTrunk · #4 07-22-2008, 12:45 AM

I know of the issue with the ac lines but when i put mine in there was no problem with clearance. I can take a pic of mine in the morning if it helps you. The alternator must go in from the top though. The stock one comes out the bottom but the al129x must go through the top. You have to disconnect the small coolant line and move it to get it down there.

lowriderdog37 · #5 07-22-2008, 10:02 AM

Pictures always help. I wanted to make this as smooth as possible, heading off potential problems before I get started. Thanks for the ideas.

pawoSD · #6 07-22-2008, 12:14 PM

Someday I also plan on doing this if I can find a good condition 129X for a LOW price.

A la junk yard....

lowriderdog37 · #7 07-22-2008, 01:00 PM

Well, it looks like I might be waiting for another week to get mine. My local indy I was going to get the alternator from isn't going to give me the core refund from my stock part. I found a guy on ebay that sells them for a good bit cheaper than my indy, so I'll try and be patient and wait.

I checked all the local junk yards, and not only did none of them have one, but they weren't even any Saabs there.

BoomInTheTrunk · #8 07-22-2008, 06:53 PM

First Picture is from the top. The Two older wires are the power + side. The larger 4 gauge wire is also Positve +. This large wire goes to the hot side of the starter. The wire is there to help compensate for more amperage. The new red wire is just spliced into the older blue wire which is the excite wire for the idiot light. The blue(red) goes to the smaller post on the alternator while the larger go to the larger. If you dont have a crimper to crimp larger gauge wire find some one who does. You cant just use a vise it wont work and wont make a great crimp. welding supply or car audio places will have the crimps and they will do it very cheaply. Alternator must go in from the top, wont go in from the bottom, although the old one will.

I found it easier to make all the connections before putting it in.

lowriderdog37 · #9 07-22-2008, 09:16 PM

Thanks for the pics. What size power wire did you use for the main connection?

BoomInTheTrunk · #10 07-22-2008, 09:22 PM

Quote:

Originally Posted by lowriderdog37

Thanks for the pics. What size power wire did you use for the main connection?

4 gauge

Mark DiSilvestro · #11 03-23-2011, 02:16 AM

Awhile back a friend gave ma a couple of used Bosch alternators that were cluttering his garage. One was a 55 amp unit that wound up being a replacement for the dying Pep-Boys rebuilt in my 240D.
The other was noticeably larger but had no factory Bosch label, just a decal from a local rebuilder.
Last week the 65 amp alternator in my '84 Euro 300TD died, with the charge-lamp remaining on when the engine was running. Inspection of the old regulator revealed badly worn brushes, but a new regulator didn't cure the problem. So I decided to install the larger Bosch unit. Of course, this alternator needed a different hookup to connect the B+ stud to the B+ at the starter. I used a 6-guage yard-tractor cable. Otherwise the alternator fit OK, once I discovered I needed to mount the upper adjuster-bracket to the alternator first, before installing it in the car. Even the belt worker out OK. Though, when I started the car, this 'new' alternator wouldn't charge either, but the new regulator saved my original 65-amp unit, fixed that.

A question - without the original Bosch label, is there any way to tell exactly what size alternator I've installed? I suspect it may have been left over from one of my friend's W107 380SL projects. I'm guessing it may be around 80 to 100 amps.

Happy Motoring, Mark

dudemanstan · #12 03-23-2011, 02:29 AM

i did the swap when i had my '80 300TD (n/a), fit fine. you may need to change belt size due to slightly different positioning, but thats about it iirc. i used two 8ga wires i think, wired straight to the battery.

Mark DiSilvestro · #13 03-23-2011, 09:39 AM

Quote:

Originally Posted by dudemanstan

i did the swap when i had my '80 300TD (n/a), fit fine. you may need to change belt size due to slightly different positioning, but thats about it iirc. i used two 8ga wires i think, wired straight to the battery.

I got lucky with the belt. Despite the larger alernator, it was just long enough to fit without being too tight. To keep the upgrade simple and less obvious, I ran the heavy cable direct to the starter. I also needed to rotate the 'clock-position' on the case to better position the terminals. Still need to make an insulated clip to secure the cable at the intake brace, and keep it from drifting too close to the exhaust.

The big challenge was removing the old alternator, as the bottom bolt was rust-welded into the aluminum bracket. Figure it took at least an additional two hours removing the old alternator with the bracket, then alernately working the bolt back & forth with a breaker-bar and impact-gun, along wiih heavy doses of oil, until it finally came free. I really dreaded the idea that I would've had to drill that long bolt if it had snapped!

Decision remains on whether to make a small bracket to secure the original harness at the alternator and keep the short jumper-wire I made for the charge-lamp, or cable--tie the harness at the inner-fender and run a longer wire.

Happy Motoring, Mark

leathermang · #14 03-23-2011, 11:21 AM

Quote:

Originally Posted by 81Wagon

The back of the alternator can be rotated....

For future reference when talking about things mechanical this is called " clocking".... we want everyone to expand their mechanical sophistication as time goes by so we look good on other forums we might visit...
LOL

vstech · #15 03-23-2011, 11:26 AM

Quote:

Originally Posted by leathermang

For future reference when talking about things mechanical this is called " clocking".... we want everyone to expand their mechanical sophistication as time goes by so we look good on other forums we might visit...
LOL

also keep in mind, when you reference "clocking" that it applies to most things with round base.
In addition to alternators, you can clock a turbo, and starter housings as well... sometimes!