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Old 12-25-2002, 12:28 PM
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Installed a 143A alternator in my W124 (86-95 E-class) - with photos

Installed a 143A alternator in my W124 (86-95 E-class) - with photos

Hi all,

This is not a "question" post, this is just a summary of what I did to my car, and thought it might help others as well. Due to large bulbs in my Euro lights and a hefty stereo planned, I needed more output. I picked up a 143A alternator from a 1998 S420 and experimented with it. I swapped my original pulley onto the 143A unit because the S420 pulley didn't stick out far enough. Otherwise it bolted right up - same mounting brackets, bolt spacing, everything. The new unit is larger and comes pretty close to the lower radiator hose but doesn't touch. So how does it perform? Read on:

I got the car fired up and tested the alternator output. Remember, my stock unit was 70A and had what appears to be two 10-gauge wires to the junction block near the battery. The new one is a 143A with a zero-gauge cable to a new distribution block and to the battery. I tested full load by turning on every electrical item I could, measured voltage with a Fluke 12 VOM, and current with a Fluke 36 DC clamp meter. All tests were done with a "hot" alternator, after driving the car at least 15 minutes with a decent load.

The stock unit could only cough up about 45 amps at idle, but did put out around 75amps maximum (revved up to ~2000 rpm). Voltage was poor... Never got higher than 13.6-13.7 volts even under light load or no load. Under moderate load it drifted down to lower 13's, and at peak load it went below 12 volts (!) as the alternator simply could not put out the power.

The 143A unit could put out roughly 100 amps at my ~600rpm idle speed, and appeared able to put out max current at barely above idle, not even 1000rpm! The highest load I could generate, including some current to charge the battery, was 125-130 amps. At 1000rpm, it put out the 130 amps and did so at 14.1 volts! And at idle, same thing, 14.1 volts (with a smaller load, under 100 amps.) The only time voltage dropped was with VERY high load at idle and I don't think I ever saw it go under 13 volts, and that was with an "artificial" load that is unlikely to occur in normal use.

My "normal" load is low beams (90Wx2) and ACC fan, plus whatever the chassis electrical stuff pulls (EDS, gauges, etc.) This appears to be roughly 40 amps, plus some current to charge the battery. The good news is, with my "normal" load I get a solid 14.1-14.2 volts, even at idle! VERY nice. I'd like the voltage a bit higher (14.4-14.6) but there is not an adjustable regulator available for the 143A unit (AFAIK). No big deal, I'm happy with the setup as-is. The stock unit badly needs an adjustable regulator, and I'd highly recommend one for those of you not interested in the full big-alt swap. Set it when stone cold to 14.6v or so, it will drop a bit as it gets hot, and you want to set the HIGHEST point.

The only down sides are extra weight and horsepower loss. The 70A unit weighs about 11.5 pounds, the 143A unit is 16.8 pounds. Not a big deal. But when you spin the shaft of the 70A unit, it feels light and spins easily. The 143A is MUCH heavier (massive) and definitely takes some extra crankshaft power to spin, even with no electrical load. I'd guess it could easily sap 3-5 HP more compared to the original. Still worth it, IMO.

Verdict: Would I do it again? Yes. I already bought another 143A unit & new pulley, and plan to install that on my other 1987 300D in a few months! For the record, a used 143A unit can be bought used for ~$75-125 or so. The donor car must be a 1996-1999 S or SL class with a V8 (SL500, S420, etc.) Others may work but I don't know what years & models, and most others are smaller (100-120A).


Photos of everything are here (nothing new from last time though):
http://www.w124performance.com/images/W124_stereo/

Only one of the photos would squeeze past the ShopForum 65k/800x600 size limit, so you'll need to click the link above to see the rest of them!


Regards,

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Installed a 143A alternator in my W124 (86-95 E-class) - with photos-alt_installed.jpg  
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Last edited by gsxr; 05-14-2007 at 12:55 AM.
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Old 12-25-2002, 01:01 PM
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Thumbs up

Dave,
Great write-up! Thanks for taking the time to post about your upgrade
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Old 12-28-2002, 02:46 AM
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Dave,

thank you for the write up and the photos!

I'm considering of installing a larger altenator into my Tea-Wagon to feed the battary for the additional heating device during winter. I had to jump start her twice in the last days and that is definitely not a luxury feature :->

Let me ask you, where are the regulator and the brushes located at these 115A and larger altenators? Under the black plastic cover or external? Is the regulator as easy to replace as at a 70A altenator?

thank you in advance,
bis denn,
Christian

1989 300TE
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Old 12-28-2002, 10:56 AM
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Hello Christian,

The regulator is internal, and looks the same as the smaller units, but is a different part number. There are 3 screws holding the black plastic rear cover on. You remove the cover and the regulator is visible, held in with 2 screws. It should be simple to replace as long as you have room behind the alternator for a screwdriver. Good luck with your upgrade, if you try it...


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Old 12-28-2002, 11:51 AM
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Dave,

thank you for the answer.

>Good luck with your upgrade, if you try it...

it depends on the result of an ebay auction, ending on January 1st

bis denn,
Christian

1989 300TE
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Old 01-29-2003, 10:37 AM
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100A altenator in my W124 300TE

Dave,

I didn't get the 115A altenator on January 1st - but some days later i bought a 100A altenator via ebay.de that looked exactly like the 100A on your photos.

The outside looks used but the inside is new. Maybe it layed somewhere in the corner for some time... I got i for 86Euro plus 6Euro p+p

Last Sunday I installed the new altenator that replaced my stock 70A one and made new wires from altenator B+ to the battery. Your writeup and the photos you took helped me a lot - thank you again.

I didn't need to change the pulley.

My old altenator behaved exactly like yours:

Quote:
Never got higher than 13.6-13.7 volts even under light load or no load. Under moderate load it drifted down to lower 13's, and at peak load it went below 12 volts (!) as the alternator simply could not put out the power.
The 100A fortunately does nearly the same than your 143A: 14.1V cold at idle, 13.8V warm at idle, not lower than 13.5V at idle even with full load I don't have a clamp meter so I can't messure the ampères...

I don't think that the voltage should be more than 14V in the system because that is the original design. The bulbs will go earlier with (lots of) more voltage as will do the other electrical and electronical componets.

The 100A is not as heavy as the 143, but it is heavier than the 70A of course. It spins easily and I don't think it will eat much additional power if no electrical power (output) is needed.

After all: It's a great improvement!

thank you again,
best regards,
bis denn,
Christian

1989 300TE
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Old 01-29-2003, 11:28 AM
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Hi Chris,

Glad your upgrade went well! It sure is nice when things go smoothly, eh? About the voltage, up to 14.4-14.6 should be perfectly safe and not cause any problems. You are correct that bulbs will have a shorter life span, but to me that's an acceptable sacrifice for the increase in light output. IMO, the danger point would be 15 volts or more. Some hybrid battery types, including Optima, require 14+ volts and really should have at least 14.5 or so. There is a really good article on this topic here:

http://www.landiss.com/battery.htm

On a side note, I have noticed no horsepower loss due to the higher rotating mass of the big alternator. You are correct, as long as the electrical load is low, there should be minimal extra drag on the crank. It will still make the engine spin up slower simply due to rotating mass, kind of like a heavy flywheel. But IMO the effect is negligible. I still plan to install the other 143A alternator on my other car, but I need to do the timing chain first!



Best regards,
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Old 01-29-2003, 12:11 PM
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Dave,

Quote:
It sure is nice when things go smoothly, eh?
Yes, it is! Last week I changed the lambda sensor. To my suprise it came out easily, in one piece and the threads in the exhaust are still good

Concerning the voltage: I agree that the additional light output is well worth the shorter lifespan of the bulbs. I wired relais into the low- and high-beams last summer and the improvement was really visible. My daughter asked me to switch off the high-beams in town With the higher voltage from the new altenator the light is even better.

The rotating masses... the additional mass of the larger altenator is nothing compared to the mass of the other components, for example the filled torque converter an so on...

All the best for your timing chain project.

bis denn,
Christian

1989 300TE
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Old 02-07-2003, 07:54 AM
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I'd like to share the pics of my voltmeter before and after the altenator swap.

This is the voltage with warm engine, idling, lights on with the old 70A altenator:



And this is the same situation (at the same stop light) two weeks later with the new 100A altenator:



bis denn,
Christian

1989 300TE
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Old 02-07-2003, 10:06 AM
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Looks good, Chris! Glad it worked out well for you too.
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  #11  
Old 02-08-2003, 11:32 PM
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wow where did you get that voltmeter ? i want one
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Old 02-13-2003, 04:14 AM
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John,

Quote:
Originally posted by johnp123
wow where did you get that voltmeter ? i want one
please excuse me, is that a serious question? Maybe I'm missing something?

In case it is a serious question
This is a standard VDO voltmeter, 52mm diameter, mounted left to an engine oil-tempmeter at the place of the original ashtray
The price is about 30 Euro in Germany and it is available at nearly every parts shop. There should be similar voltmeters from manufacturers like Motometer.

hope that helps,
bis denn,
Christian


1989 300TE
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Old 10-30-2003, 03:40 PM
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FYI, I just picked up a 150A alternator. It's even larger than the 143! I'll take some photos of them side by side. I'll be installing the 150A on my other car, and will do some testing to see if it performs any better than the already fantastic 143A. I think it will still fit, most of the size difference appears to be front to back, but I'll know for sure when I try to bolt it up. Stay tuned, I should have it done in a few weeks...

(now, if I could just snag that 180A alternator from the E55 AMG... )
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Old 10-31-2003, 11:15 AM
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GSXR,

Could you post the part # and the MB model and year it might be available.
I believe I will be doing this in the near future as well.

You mentioned new distribution block and 0/1 wire, could you please elaborate.

Thanks,
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Old 11-01-2003, 04:02 PM
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Wow, This is a great mod! Thanks for the info gsxr. Ill be doing this one for sure! Do you happen to have a part number for the new distribution block?
Thanks!
Adam

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