Alternator upgrade - PeachParts Mercedes-Benz Forum

lsmalley · #1 03-19-2013, 05:48 AM

Which MB (year and model) has a higher amp alternator that will fit a 1990 190E without making any modifications? Basically a direct bolt on. Also, what are the pros and cons, if any, of upgrading to a higher amp alternator?

JamesDean · #2 03-19-2013, 08:11 AM

140 S420/S500, mid 90s
124 E420/E500, mid 90s

Both have higher output alternators I believe.

Pros: more power obviously
Cons: none that are notable. Might have to re-clock alternator

Both my 124 and 201 have upgraded alternators. The 201 has a 143 amp the 124 has a 150amp. Just be sure you swap the pulley over to the new alternator.

oldsinner111 · #3 03-19-2013, 08:57 AM

I know if I upgrade my w126 over 80 amp I have to run heavier wiring from alternator

JamesDean · #4 03-19-2013, 09:17 AM

Yes. You will need to upgrade the wiring from the alternator to the distribution point / battery. Probably an additional $15-20 on top the cost of the alternator.

lsmalley · #5 03-19-2013, 03:53 PM

Heavy wiring?? What do you mean? Any pictures or links for this?

JamesDean · #6 03-19-2013, 04:05 PM

You'll need to replace the wire that leads from the alternator to the distrubition block or battery. The factory wiring is two 10 AWG wires (I believe) you'll need to replace that with a thicker wire that can handle the higher current output of the alternator. Preferably 2AWG or smaller. If I remember tonight I'll get picture from my 190E/300D/420SEL.

lsmalley · #7 03-19-2013, 04:08 PM

Thanks

Frank Reiner · #8 03-19-2013, 04:45 PM

Before changing to a higher output alternator, it would be in order to determine what additional demand is being placed on the generating system. The 126 cars of the same era with seat heating, rear window heating, larger fan motors in the HVAC system, and greater ignition and fuel pump demand, all operate with reserve capacity with an 80A (1120W) supply.

lorainfurniture · #9 03-19-2013, 10:20 PM

Gsxr has a fantastic write up on how to do this. It's much easier than you think. Now I can nearly blow my trunk lid off with my jlw7-3 and the amp won't cut out. Still dims the dash lights even with a 150a alternator.

Use the search button

lsmalley · #10 03-19-2013, 10:31 PM

Quote:

Originally Posted by lorainfurniture

Gsxr has a fantastic write up on how to do this. It's much easier than you think. Now I can nearly blow my trunk lid off with my jlw7-3 and the amp won't cut out. Still dims the dash lights even with a 150a alternator.

Use the search button

found it. thanks.
http://peachparts.com/shopforum/car-audio-multimedia/53236-installed-143a-alternator-my-w124-86-95e-class-photos.html

97 SL320 · #11 03-20-2013, 08:22 PM

Some high amp alternators put out less power at low speeds than a low amp alternator. ( I remember looking at amp / RPM curves for 80's GM Delco single stator units. )

Some Japanese units ( Mitsubishi for one ) have 2 stator winding sets, one is connected in a Delta ( triangle shaped hookup ) and the other set is in a Wye ( Y shaped hook up ). Each is connected to it's own diode bridge then the pos and neg are paralleled. One of these windings has better low speed performance and the other has better high speed. Paired they smooth out the output curve.

I'm pretty sure the later plastic backed Bosch units are delta - wye .

Before you make a alternator change, hook a volt meter to the battery and drive the car for say 10 minutes without any accessories on. While still running the engine at road speed, take a reading, this will be your at speed reading. Let the engine idle for a minute and take a reading, this will be your idle base line. Charging systems typically run 13.8 - 14.2 but each car will vary a bit. We are checking at the battery to eliminate any voltage drops at the end of a long loaded run.

Next, do the same with a normal accessory load. And for worst case, turn on everything.

You will find that, at idle with a load, the voltage will drop. If it does not dip below 12.66 ish V, you have just enough alternator. If at speed the voltage is much below 13.5 ish V, you don't have enough alternator.