Refreshing the alternator on an OM617 - Page 3 - PeachParts Mercedes-Benz Forum

whunter · #31 08-27-2011, 04:19 PM

Thanks "Army" this DIY is now in the wiki.

Refreshing the Alternator on the 1981 300D (OM617 W123) * by Army 2/24/11
http://www.peachparts.com/Wikka/OM617Alternator

Stretch · #32 08-28-2011, 05:34 AM

You're very welcome - I hope it helps.

ITGuy · #33 02-08-2017, 03:41 PM

Great write up! But if there was a view of the diodes I missed it. Did you see them? I am wondering if it is possible to put in faster diodes and little capacitors to reduce the radio noise (which is already nice and low on these cars)?

Mxfrank · #34 02-08-2017, 04:40 PM

The rectifier bridge is on the back of the stator. Replacing the diodes is not an amateur job. Not a clue what you mean by "faster diodes", alternator diodes are alternator diodes. Most (not all, but certainly most) Bosch alternators have a tap for an external suppression cap (See photo). You can always add one to the D+ post if necessary.

A few comments on this write-up:

- Anytime you are soldering inside an alternator, you need to use a high temperature solder. 60/40 is iffy because the temperatures can really get up there.

- removing the rear bearing is easily accomplished with a jaw-type bearing puller.

- The four screws that hold the front bearing plate in place are TOUGH to get out, due to corrosion. I usually just drill out the heads. You don't have to drill through the screw, just drill into the head with a large drill until head pops off. Then remove the cover and the stubs of the screws can be removed with vice grips.

- The front bearing is tougher to pull, because you can't get a jaw puller between the bearing and the metal plate. What you need is a collar type puller, see photo. If you buy a front bearing kit from an alternator supply house, you will get a new plate. If you buy a loose bearing from anywhere else, you will have to reuse the old plate, so be careful with it.

- There are two wires that snake up out of the rotor coil and connect to the rotor assembly (see photo). These wires are epoxied to the rotor claws at the factory, and the epoxy is oven baked. Before you put that rotor back in, you want to inspect these wires, as they are the no 1 cause of rotor failure. If the epoxy is compromised, or if the wires have become loose in their sleeves, you want to apply a coat of JB Weld to hold them in place. If the adhesive fails, the wires will be torn apart by centrifugal force and that will be it for this alternator. Also make sure that the insulating sleeves aren't damaged.

- I have no idea how the slip rings are replaced, this secret of how they are secured is closely held by rebuilding shops.

Stretch · #35 02-09-2017, 05:27 AM

Wow blast from the past!

BillGrissom · #36 02-09-2017, 03:14 PM

Thanks for all the great info and contributions. I love rebuilding components when I can get the parts and the PN's helps. I am suspicious of store-bought rebuilts, as some don't even work out of the box. I still regret paying $120 the first time I replace a M-B alternator (vs $28 w/ lifetime warranty for my 60's Chryslers). It had bad bearings which locked the rotor. Those pressed-in diodes should get good cooling and last a long time. Early Chrysler alternators had that and rarely fail, unlike later ones with 3 diodes hanging in the air. I got quick at replacing those in my 1982 Aries since they vaporized every year, like clockwork.

hjoab · #37 05-07-2017, 11:55 AM

I see at the pictures that you haven't removed any capacitor. The set of parts has no one. Nor have you added a new one when you resembled it back. :confused. At this link you can see it and where it goes at step 8:

1985 300D Alternator Replacement Procedure - Mercedes-Benz Forum