300E... Sick Alternator - PeachParts Mercedes-Benz Forum

Jim Marshall · #1 06-01-2006, 12:18 AM

I have a 1989 300E, and we're on to its third alternator. Is there a way of replacing the stock alternator with a high amperage unit?

haasman · #2 06-01-2006, 01:17 AM

Are you sure it is a bad alternator and not the small voltage regulator attached to the unit on the back side?

Haasman

#3 06-01-2006, 01:24 AM

Quote:

Originally Posted by Jim Marshall

I have a 1989 300E, and we're on to its third alternator. Is there a way of replacing the stock alternator with a high amperage unit?

what brand are you using?

GVB · #4 06-01-2006, 02:04 AM

Bosh has really bad alts. If I have to use a Bosh, I order 2 just in case. Make sure your batt. is ok though. An alternator will not charge a bad Batt.

#5 06-01-2006, 02:18 AM

Bad bosch? speaking from a shop stand point where we replace several a year, during the past year we have only seen 2 bad bosch reman units, i think that is pretty good,
the one thing i think is bad is that they use used regulators, they do install new brushes, but the regulators have been the cause for the failures we have seen with the reman units.

GVB · #6 06-01-2006, 02:24 AM

Yeah, bad bosh. The quality of bosh has gone down hill for the past eight years or so. The one that I took to my mom and pop's alt shop that I use for specialty needs, was a bad armature. Go figuar, huh.

Zeus · #7 06-01-2006, 11:27 AM

Quote:

Originally Posted by Jim Marshall

I have a 1989 300E, and we're on to its third alternator. Is there a way of replacing the stock alternator with a high amperage unit?

Jim -

If your 300E has the stock 70A Bosch alternator, I would definitely upgrade it. I upgraded mine to the 80A Bosch AL66X alternator. It's not just the fact that it outputs an extra 10 amps, the 80A version is much more efficient at lower RPMs.

I've posted info from one of my previous posts below -

Quote:

Originally Posted by Zeus

The problem has been solved! Thanks again to everyone who replied and once again, to this forum in general.

I replaced my ailing stock 70A alternator with a new Bosch 80A (66X) alternator. All symptoms are gone now. Cars runs perfectly.

I did some before and after battery multimeter readings right before I did the swap -

BEFORE (70A):
rest - 12.85V
idle - 13.86V
idle with full load = 11.87V
full load, 1500 RPM = 11.74V

AFTER (80A):
rest = 12.88V
idle = 13.97V
idle with full load = 13.56V
full load, 1500 RPM = 13.94V

A few other unexpected pleasant surprises awaited me as well - I had an annoying flicker of my instrument panel lights at idle - totally gone. Lights are all nice and bright. The monowiper now zips across the windshield crisply and the washer jets spray properly.

It was easy to install the new alternator. 2.5 hours total. Old one came off easily and I took it off without removing the serpentine belt. I loosened (but not removed) the fan shroud and I just loosened the two mounting bolts (13mm) and the old alternator slipped out. I cut the old wiring harness near the base and there were three wires - two 10 gauge wires and one smaller (16 gauge?) wire. I soldered new eyelet connectors to each wire and sealed with heatshrink. The 80A (Bosch 66X)alternator doesn't have a plug in harness, it has a large bolt and a small bolt to attach the wiring (see picture here in the Fastlane catalog). The two large wires go to the large bolt and the small wire to the small bolt. That's it - thanks to M.B. DOC for that info in another post!

To install the new alternator, I slipped it roughly into place and got the belt on the pulley first. I then attached the upper mounting bolt. Then, from underneath the car, I pulled down hard to get the alternator into place for the lower mounting bolt. It took some strength, but I'm no Hercules (no pun intended) and it wasn't that hard. I had the lower bolt ready in place, so once I had leveraged the alternator into position, I slipped the bolt home and tightened it. That's it, no removal of the belt necessary - not sure if everyone is this lucky, I'd hate to mess around with the tensioner. Belt tension is fine (and the serpentine belt is in good condition in my car, btw).

So that's it, I've got a new alternator, a happy Benz and a great new project to look forward to - installing my new Alpine amp. That's a post for another section though. Life is good!

Thanks again to all!

Chris

More info, courtesy of M.B.DOC -

Quote:

Originally Posted by M.B.DOC

The charging system on the 1986-89 W124 chassis is under-powered. IN 1990 MB installed a much more powerful alternator. AT dealer & many indenpendant shops that early 65-70A alternator is replaced by the later 80+A alternator. The only part needed to install the larger alternator is the wiring loom MB part number 124-543-45-26. The alternator is 008-154-48-02-88 OR Bosch AL66X

Jim Marshall · #8 06-02-2006, 06:00 PM

It was a Bosch rebuilt and it was installed with a new battery.

I like the idea of a heavier duty alternator. Of all the cars anc company vehicles I have owned this is the only one that I have replaced an alternator.

Jim