Alernator capacity on various Mercedes' - PeachParts Mercedes-Benz Forum

otto huber · #1 03-07-2004, 04:27 AM

I own a '79 240D, and need to find an alternator that can handle an electric in line fuel heater. The heater that I will be using, draws as much as 40 amps when first turned on, then regulates itself as the fuel temp gets warmer.
Are there any later model Mercedes' with alternators that could handle that load. I was told that these heaters have been wearing out the stock alternators on these cars. Thanks for your help.

Otto

TomJ · #2 03-07-2004, 10:31 AM

There is a "high-ouput" direct replacement Bosch at 65 amps (check Fastlane and others), but....

Someone posted a link of a fender-mounted regulator that allowed the stock alt to run higher amp output (basically trash the alt-mounted reg and replace with a F**d/Ch*v reg), now if I could find that link.....

Brad123D · #3 03-07-2004, 11:33 AM

I suggest searching some sites that supply equipment for high powered automotive sound systems.

TomJ · #4 03-07-2004, 12:09 PM

Here's the link I was thinking of that someone posted about mods to alts:

http://www.turbobricks.org/mods.php?content=alternator_ext-reg

dieseldiehard · #5 03-07-2004, 01:39 PM

I believe the 80 Amp Bosch AL69X is what you need. It is used on the W126 cars and is I believe the largest model available that will be similar to the one used in the 240D. You may find it has a different pulley, the twin v-belt pulley used on the higher output alternator isn't going to be necessary on the 240D but will be useable OK.
There are 115 A alternators (maybe even higher) on late model Mercedes but they won't fit your brackets. They all use serpentine belts nowdays too, making retrofit a big problem.
Goodluck!
DDH

jbaj007 · #6 03-07-2004, 02:51 PM

I use the AL69X on my 300SD with a Transpo IB373A 14.4 volt adjustable regulator and am very happy with the increased amperage available for the electrical accessories I've added.

http://www.transpo.de/catalog/US_cat.html

Go to regulator>bosch>IB373A and you'll see what I found to be a fairly easy solution.

On the AL69X swap, I believe there was a slight belt issue, that was easily dealt with (1035 vs. 1000 belts comes to mind).

#7 03-07-2004, 02:55 PM

The alternator for my 300SDL is 70 Amps. Another forum member mentioned to me that an alternator out of a newer S320 would fit my SDL, and that particular alternator is 150 Amps. I don't know if either alternator will fit on your 240D, but it's worth checking into.

190D22 · #8 03-07-2004, 03:39 PM

I would tend to lean towards something under 80 amps and above 60 amps for our little diesels. The 143A alternators found in the new V8s I feel will rob a lot of HP from our already lacking engines. My stock 55A handles my subwoofer fairly well, only with rap music and w/ the blower on full do I see the headlights dim.

One thing you might want to consider is putting a big (around 1 farad) capacitor on your heater to take care of that in-rush current. I need to put one on my amp.

whunter · #9 03-07-2004, 08:39 PM

Hello Everyone
MB diesel, can handle a 250 amp alternator.
Your mileage will suffer!!!
The alternator can take up to 35 HP at full output.
The pulley is easy to change between serpent and V belt type, making retrofit no big problem.
Brackets are more annoying.

otto huber · #10 03-08-2004, 03:54 AM

Thanks guys for all of your helpful advice. I'll probably go digging through the junk yard and try to find a fresh AL69x first. The fender mounted regulator sounds good too.

Take care

Otto

mandrake · #11 02-19-2005, 01:44 PM

Best thing that I have done for my electrical system is to purchase an "OPTIMA" deep cycle battery.

No more problems using the stock 35 amp alternator.

I even use an electric fuel pump to push the fuel to the supply pump.

dieseldiehard · #12 02-19-2005, 02:12 PM

A battery as big as a house isn't a solution if you are loading the system with say a WVO heater that draws 20 A plus a pump (8 to 10 A) and the other normal system load (18 to 20 A). If that total exceeds the output of the alternator then the alternator won't last long because the diodes and windings (usually the diodes go first) are stressed out and run hot. The current from the battery is only part of the source, the alternator contributes more because the load (pumps, lights, radio, etc) causes the battery potential to drop, then the regulator kicks in and the regulator ramps the alternator up. The current comes from the highest voltage source and the alternator, being say 14.1 V sources most of the current because a battery is a 12.8 Volt source by its nature.
A larger alternator is really desirable whenever the load is massive, and using a higher voltage regulator makes the alternator supply more current and charges the battery to a higher potential. 14.1 or 14.5 V regulators are available from Transpo and can replace the existing regulator on some MB alternators to great advantage.
Contrary to common opinon, a higher current alternator will not raise fuel consumption or drain the power from an engine, UNLESS the load on the electrical system is more than the stock (original) amount (plus or minus a few amps). When you put a big WVO heater and pumps or some big audio amplifiers and speakers and make a thumper, then of course you are loading the system, and HP is necesary to feed the electrical load, and fuel is necessary to feed the engine and so on a and yes, then the situation is quite different
(btw I hate thumpers!

)

rg2098 · #13 02-19-2005, 02:47 PM

Quote:

Originally Posted by whunter

Hello Everyone
MB diesel, can handle a 250 amp alternator.
Your mileage will suffer!!!
The alternator can take up to 35 HP at full output.
The pulley is easy to change between serpent and V belt type, making retrofit no big problem.
Brackets are more annoying.

Large alternators will only zap more HP as they are worked more. That 250 amp will only take 35 HP when its running at full capacity.

MTUpower · #14 02-19-2005, 05:10 PM

do a search on AL129X- you'll find the thread about the 115 amp alt that has a successful track record in w123's. I've got one now, and untill I pull another, it's not for sale. They come up in the yards here often, but are no fun to pull.
William

jayb79 · #15 02-19-2005, 06:21 PM

In my search for the alt i just replaced in my 86 300td, i found that the only difference in any of the alts for any benz is the pulley and the wiring. i looked at a lot of cars from the late 70s 240 up 190s from the early 90s. the mounting lugs are the same on all. any alts over 70 amps have a stud to feed the power to the battery the others have 2 large spade terminals. i ended up getting a 70 amp unit off of a 89 190 with a 4 cyl gasser in it for $25, it look like a new reman and it bolted on with no changes.