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'91 560SEC, '98 SL500
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1,974 Posts
Discussion Starter #1 (Edited)
Hey Guys - Some of you warned me that with the electrical draw of the twin electric fans that I recently installed I might be pushing the capacity of my stock 80Amp alternator.

The other night for grins, I did a "load" test with the A\C running full blast, electric fans on, wipers on, fog lights on with high beams, stereo on (I have an aftermarket stereo installed) etc, the 80amp alternator just could not keep-up.

Consequently I bit the bullet and bought a new 150Amp alternator and installed it. I tested it with the same electrical load / draw and the new mini electrical substation handled the load with no issue.

This 150Amp alternator has a larger / wider stator, rotor and subsequent windings, as large as you can fit in the stock housing. To mange the additional heat the alternator housing has holes on the outer diameter. The weight of this alternator is the same as the stock 80amp unit and the cost is $220.

This is a good option for a few extra bucks over a re-man stock unit.

Onto the pics:






Yasin
 

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Premium Member
1980 450SL; 1984 500SEC Euro; 1991 560 SEC
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345 Posts
Yasin,
Thanks for this, great information and timely, as I hope to install a new stereo in a bi-amp set up so I will be pulling some additional amperage as well. I am considering the electric fan setup but probably not until next year as cooling will soon be no issue here. Ha.

Thanks again.
 

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1989 560SEL, 1979 Cressida MX32, 2006 F150 Lariat
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1,510 Posts
I have 3 80amp units stored in a box and 1 still on the 5.6 engine in the garage. With all of the recent electrical gadgetry I've added it maybe a good idea for me to trade one of them in on a 150amp unit.

Where did you get this one from?

Thanks for sharing.
 

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1990 560 SEL
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731 Posts
The 560 SEL, it has an electric fan and a clutch fan. I'm assuming it's the same for a 560 SEC. Did you remove the clutch fan and install a second electric fan?
 

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'91 560SEC, '98 SL500
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1,974 Posts
Discussion Starter #7
Taylor - Yes I removed the clutch fan and installed twin Flex-A-Lite pullers:


I have a detailed thread from a month ago (or so) on this install.

Yasin
 

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2012 CL550 4MATIC Coupe
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9,992 Posts
THAT'S SO FUNNY! I JUST replaced my HD alternator with this one on Friday!

Yeah, this is a REALLY good mod if you are going to install Aux Electric fans. I did the upgrade last year when I was doing my engine rebuild because I upgraded the single fan that SEC's have to factory SEL twin fans and I estimated the instant on draw at 30-40 amps, and I had planned to use a W203 Single fan unit that draws 30 amps on it's own, and so that was minimum 60 amps draw alone. With a factory 80 amp unit, you can see there's not much left to run the car on.

Once you start turning on the accessories, and if its a hot day (like here) and the fans come on (especially if you did the twin fan mod!) there is a really heavy draw on the alternator. You would be surprised at how much load the A/C system puts on the Alternator! I had a bad alternator which worked fine until you put the AirCon on. Then it would drain the battery and the car acted like the Alt was bad altogether. It was putting out just under 12 volts.

What this did was put a critical drain on the electrical system, which in turn starves the electric fans. They run slower and hence do not push enough air through, and the car starts to overheat. If you have an all electric fan system, then you are really screwed. If you still have the mechanical one on the front of the motor at least you are still pulling air through. But if the fan clutch is bad, or you replaced it with and electric like Yasin did, then they are not running to capacity, and you can fry your motor.

So this is a very important upgrade if you are adding ANYTHING that draws significant power.

So I ordered this one too last week and popped it on Friday and all systems run at full capacity under a very heavy heat load. I put on a new fan clutch too while I was at it, just to be sure.
 

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Make sure that, once installed, the pulley of your new alternator lines up perfectly to the plane of the rest of the pulleys. The previous owner of my W126 did the same 80 - 150A upgrade and the pulley of the one does not line up with the rest. The result is a terrible noise every morning on cold start when the belt is cold and rigid.

Sent from my HTC One X using AutoGuide.Com Free App
 

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'91 560SEC, '98 SL500
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Discussion Starter #11
Make sure that, once installed, the pulley of your new alternator lines up perfectly to the plane of the rest of the pulleys. The previous owner of my W126 did the same 80 - 150A upgrade and the pulley of the one does not line up with the rest. The result is a terrible noise every morning on cold start when the belt is cold and rigid.

Sent from my HTC One X using AutoGuide.Com Free App
Everything is normal and the pulleys line up perfectly, I drove 30-miles after the install and happy to report all is well.
Yasin
 

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Premium Member
1991 560 SEC 1994 E500 2014 E350 Cab
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7,029 Posts
Mine gets delivered Thursday. I was going to Bermuda Friday to celebrate 20 years with my wife, but some Hurricane named Leslie is changing all that! I guess I will piddle with a new alternator LOL instead!
 

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Premium Member
1991 560 SEC 1994 E500 2014 E350 Cab
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7,029 Posts
well greasing up my rear windows I had the doors open so I didnt melt in my garage in South Texas. I could barely start my car as the lights had been on for 2 hours in a skiddish battery. Managed to have enough to start the car, but within minutes, all of the warning lights came on the display and beeping etc. my battery must be toast it will not hold a charge.
 

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1985 300SD with a bad transmission and a 1985 300SD with a good transmission
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578 Posts
Thank you! I literally logged on to ask this question in my Jalopy thread. Does anyone know if this will work in an '83 300SD? Also, how much extra HP does it take to run the 150 vs the 80amp?

Answered own question: the seller's ebay page says no, it doesn't work. Hrmm...
 

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'91 560SEC, '98 SL500
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Discussion Starter #17
well greasing up my rear windows I had the doors open so I didnt melt in my garage in South Texas. I could barely start my car as the lights had been on for 2 hours in a skiddish battery. Managed to have enough to start the car, but within minutes, all of the warning lights came on the display and beeping etc. my battery must be toast it will not hold a charge.
About the worse thing you can do to your car is start it with a weak battery..it is sudden death to any alternator.
 

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1985 380SE; 1984 500SEC
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71 Posts
My experience with the 150-Amp BNR alternator (option #2 in the OP) has not been good.

I have installed the same Flex-a-lite dual puller fans as slownrusty. (I know he's moved on since then.) The fans work very well, but this supposedly upgraded alternator cannot handle them. In a harsh test today (near 100 degree day, A/C working hard, fans on 100% and auxiliary fan also running) my in-car voltmeter barely registered 12 volts when idling. In other words, the battery was having to provide some of the power - not a healthy situation.

BNR has offered me a return, yet I found their attitude disappointing. They attempted to blame the fans, claiming that fan manufacturers often under-state the true electrical load their product will impose. But if their alternator is as good as they say, it should have no trouble handling the fans, even if the current draw is 30 Amps instead of the stated 22. And why do people purchase upgraded alternators in the first place? Generally, it's for high-end audio, or for electric cooling fans. So when BNR tells me that they often have this problem with electric fans, it seems to me that they ought to be looking at their own claims, not those of the fan producers.

Incidentally, I ran a high-quality, fine-stranded, 0-gauge copper wire direct from the battery to the alternator to give it every chance to deliver the goods. This made very little difference.
 

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Premium Member
87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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4,278 Posts
Gee that is interesting to hear Yasin?
Are they not what claimed to be or a con.
I was wondering where they would keep sourcing the parts without asking for any trade-in of your old one when purchasing.
Be interested to know more about this product as i fitted one to my white coupe.
 
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