Installed a 143A alternator in my W124 (86-95 E-class) - with photos - Page 2 - PeachParts Mercedes-Benz Forum

Zeitgeist · #1 11-20-2003, 02:30 AM

Well Dave, I may have glossed over the amount of effort I put into the alternator swap on my 220 D. It's been over a decade now, but I seem to remember dinking around with fabricating a new adjuster mount and shimming the pulley to run in line with the crank.

I guess the main point is for MB folks to think of all the Northern European vehicles out there as potential parts donors. Volvo, Saab, Audi, VW and BMW electrical parts can be interchangeable--within reasonable limits. The local pick-a-part here is usually full of Volvo 740's and Saab 900's, which have fairly high amperage Bosch alts. I think they charge $25--cheap.

BTW: Our Passat has a 120 amp alternator and is a serpentine system. Late model VW's might be a good alternative for the other OM 60X engines with serp setups.

gsxr · #2 08-21-2007, 11:53 AM

Bump for recent question... also updated links in original posts.

gsxr · #3 03-13-2008, 10:07 AM

TTT.

LUVMBDiesels · #4 03-13-2008, 01:17 PM

One comment... I was able to stick a AL129X from a Saab into my 300SD simply by swapping the serpentine pulley for my dual vbelt one. Why were you saying that it could not be done?

gsxr · #5 03-13-2008, 02:18 PM

Quote:

Originally Posted by LUVMBDiesels

One comment... I was able to stick a AL129X from a Saab into my 300SD simply by swapping the serpentine pulley for my dual vbelt one. Why were you saying that it could not be done?

I didn't say that.

I said the factory Mercedes alternators used with serpentine belts can't use the older V-belt pulley. The shafts are different. The 143A is AL0162X, the 150A is AL0766X.

The AL129X is not a Mercedes alternator, that's from a Saab. It was never used on any Mercedes. And yes, it works fine on an OM617 or M117 engine with V-belts. more details on the AL129X swap (for OM61x/M117/etc) are in this thread.

Photo of AL0766X (150A, Mercedes) - note the shaft length is very short:

Photo of AL129X (115A, Saab) - note the shaft length is much longer:

babymog · #6 03-13-2008, 02:06 PM

I noticed that the 150a alternator has a smaller pulley, did you leave that pulley on to let it spin faster at idle or did you put the stock '87 pulley on it?

I bought a 90a Bosch for the '87, smaller and lighter than the original, and without heated seats should be adequate for my uses, just wanted to get away from the low-voltage idling thing with the A/C on or all of the heated devices. It isn't as much the max. output that is inadequate (it is inadequate though), it's the low-rpm output that is dismal. Extra cycles on the battery.

Why do you want to increase your output voltage? Isn't 14.3volts excessive for a lead-acid setup? My big charger systems only use 14.3v as an "equalizing" voltage periodically, and it isn't recommended for sealed or no-maintenance type batteries as there is too much outgassing / water loss.

gsxr · #7 03-13-2008, 02:25 PM

Quote:

Originally Posted by babymog

I noticed that the 150a alternator has a smaller pulley, did you leave that pulley on to let it spin faster at idle or did you put the stock '87 pulley on it?

No, I used the stock pulley, which is the same on all OM601/2/3 diesel engines. You need to use the pulley that came off your original alternator. If the diameter is different, the belt length may need to be changed. With the original pulley, there's no problems here.

Quote:

Originally Posted by babymog

It isn't as much the max. output that is inadequate (it is inadequate though), it's the low-rpm output that is dismal. Extra cycles on the battery.

Exactly! And that's what my data showed as well. The 150A unit can put out a huge amount of current at idle, with no voltage drop like the wimpy stock alternator.

Quote:

Originally Posted by babymog

Why do you want to increase your output voltage? Isn't 14.3 volts excessive for a lead-acid setup?

The stock 70A units have low output voltage (13.6 or so), and that is too low, IMO. Some new-technology batteries must have over 14.0V to reach 100% charge. However, the output of the 143A/150A units is fine, at 14.1V minimum. If people want to keep their stock 70A alternator, they might benefit from the adjustable regulator, which could be turned up to the low 14's. The higher voltage also helps your headlight output, etc. Mid-13's is too low, IMO, but low 14's is fine.

#8 03-13-2008, 03:12 PM

Quote:

Originally Posted by gsxr

The stock 70A units have low output voltage (13.6 or so), and that is too low, IMO. Some new-technology batteries must have over 14.0V to reach 100% charge. However, the output of the 143A/150A units is fine, at 14.1V minimum. If people want to keep their stock 70A alternator, they might benefit from the adjustable regulator, which could be turned up to the low 14's. The higher voltage also helps your headlight output, etc. Mid-13's is too low, IMO, but low 14's is fine.

...or you can just use the stock alternator with an off the shelf battery and not worry about it. The stock setup is more than adequate unless you spend all your time idling or have some extra large electrical loads.

vstech · #9 03-13-2008, 03:52 PM

Quote:

Originally Posted by Craig

...or you can just use the stock alternator with an off the shelf battery and not worry about it. The stock setup is more than adequate unless you spend all your time idling or have some extra large electrical loads.

yeah extra large, like modern headlights, and seat warmers... extended glow plugs, oh, I don't know, maybe a decent stereo? yeah, those are "extra large" loads...

#10 03-13-2008, 04:25 PM

Quote:

Originally Posted by vstech

yeah extra large, like modern headlights, and seat warmers... extended glow plugs, oh, I don't know, maybe a decent stereo? yeah, those are "extra large" loads...

Mine works just fine (no seat warmers) with a stock alternator. You know, we really don't have to try to re-engineer these cars every 15 minutes, the original designers did a pretty good job.

#11 03-13-2008, 07:03 PM

OK, 12-15 amps sounds like a lot of current for that fan (thats almost 1/4 HP), but I've never checked myself. If it does pull that much it would cause a voltage dip.

babymog · #12 03-13-2008, 07:09 PM

I agree wholehartedly with GSXR. I bought my '91 TE4matic at a time when I had an '85 quattro and '85 Jetta, both had 90a alternators (stock). The new Mercedes was the only one that would idle at low voltage, to the extent that the rear-window defogger and seat heaters would shut off when idling at a light or in slow traffic, the quattro would happily power the heated seats and rear-window defogger. The weak alternator did finally give up, around 90,000miles, where the quattro alternator was still original when I sold it with just over 200,000miles.

The alternators are weak.

The second thing that happens with the low output at idle is that you are drawing from the battery. Look at what affects the capacity and life-expectancy of a lead-acid battery. It has a set number of cycles, the deeper the cycle the less of them you get. every time the car is idling and fans etc. are drawing from the battery, that's a discharge-charge cycle albeit a minimal one. More important is the proper charging. You MUST charge a battery properly, every time, to maintain full capacity. Shallow charges and multiple cycles without proper charging will degrade the capacity of the battery as the battery's plates grow dendrites and have sulfated patches that do not recover. The lead-sulfate also sluffs off and ends up in the bottom of the battery, it can endure vibration and shock best when fully-charged.

Anyway, charging a lead-acid 6-cell battery is best over 13.4v (at the battery) regardless of the current necessary to maintain it. Some manufacturers believe in a 14.3v equalization to fully boil the sulfates from the plates and expose useful lead. The more incomplete charge cycles, the more sulfates, and eventually the more irreversable damage.

In short, it is important to properly charge a battery, 13v doesn't do it, and if it is interrupted and discharging every time you hit a stop sign, you're killing your battery. For this reason, I felt it necessary to upgrade to a charging system at least adequate for a VW of the same era: the 90a Bosch. 65a is a joke.

btw, thanks G for posting this DIY, we do appreciate it. Is the 150a an ML part (looks like it says "2001 ML" in paint marker)?

gsxr · #13 03-13-2008, 07:47 PM

Excellent writeup, Jeff... all your technical points about batteries & charging are spot-on.

There are a number of donors for the 143A and 150A units, basically from late 90's and early 2000's models with M119, M120, and M113 engines. But be careful past about 2002-2004, the alternators changed somewhere in that time frame to a newer electronic 2-wire regulator, which I'm not sure is compatible with our older 1-wire setups.

Anyway, I have a spreadsheet with more info, which may help those in search of a 143A or 150A unit. Click here for the Excel version, or those without Office, click here for a PDF version. It's out of date, I need to update the info on there. Most used units are in the $75-$125 range, btw.

babymog · #14 03-13-2008, 08:46 PM

This is the 90a Bosch gleaned from a '92 190E 2.3. Looked like a new replacement, so it was worth the $20. Ring-terminal B+ instead of the spade-terminal on the original '87 65a Bosch. Roughly 11.5lbs.

Hit Man X · #15 03-14-2008, 06:19 PM

I did the 143/150A swap a while back in my SDL and 300SEL, nice upgrade for sure.