Alternator with at least 105 AMPs at idle

[motto123]

Dear All,

Does anybody know an alternator that would fit the M119.982 engine that puts out 105AMPs or more at idle? i have found this nominal 220AMP max output alternator from Bosch - AL 9415X, but the mounting doesn't fit and I cannot get a drawing of this alternator to see how I can modify it or make an adapter. I assume this one would have sufficient output at idle.

Any help is highly appreciated.

Thank you, Matthias

 

[gsxr]

Why do you need 105 amps at idle? That's an extremely high load.

The 150A factory (Bosch) units are rated for ±90A at idle but actual output is right around 100A, pretty close to what you are looking for.

Most higher-rated alternators trade peak output for idle output, so it might be tough to find something with super-high idle output.

 

[motto123]

Why do you need 105 amps at idle? That's an extremely high load.

The 150A factory (Bosch) units are rated for ±90A at idle but actual output is right around 100A, pretty close to what you are looking for.

Most higher-rated alternators trade peak output for idle output, so it might be tough to find something with super-high idle output.

Thank you for the quick response. I have two aftermarket cooling fans that need 20 amps each plus the original Mercedes fan with 30 amps that comes on when the AC is on. Plus lights, ignition, and better stereo. The 105 amps at idle is a guess. 100 amps might be sufficient as well. I could also turn the AC fan off when both cooling fans for the radiator turn at full speed. My current 105 amp alternator (max rating) is too small, as voltage on the battery drops to 12.1-12.3V at idle when everything is on. I already upgraded the wiring.

 

[gsxr]

Ah, the additional info helps. It's unlikely you would ever have all those items pulling max current simultaneously. Your 105 alternator (likely 110A-120A, there was no 105A factory alternator I'm aware of) only puts out around 60-70A at idle which is inadequate with your aftermarket fans adding ~40A peak load.

I would definitely install the 150A alternator to start with, it's 100% bolt-in. Read the entire thread below for details, installation should be nearly identical in your R129 SL500.

HOW-TO: Upgrade Alternator from 110Amp to 150Amp | Electrical, CAN and Wiring

Upgrading the stock 110Amp alternator with a 150Amp alternator from a 2001 ML55 provides an additional 40 amperes worth of potential current supply for the 500E electrical system’s consumption. Background: I’ve finally gotten around to replacing my stock 110Amp Bosch alternator with the 150Amp...

www.500eboard.co

 

[motto123]

Dave,
I have a Volvo alternator on my car.
Thank you so much for your help!
Have a great weekend,
Matthias