Alternator Rebuilding

[samiam44]

Ok,

So I was looking for an option- I put a 143A out of a S500 in my car and it broke shortly after installation(new regulator and rear bearing installed). I got a second one and on inspection- no use putting it in the car. It has severe slip ring wear, both bearings are noisy. But I still had my original (120,000 miles) alternator which is 110A. Calling Tom Hanson @ classic center, looks like MB now wants $650ish for a factory rebuild. All the online stuff seems to indicate the black box Bosch (available at local auto stores) is rebuilt in Mexico with off-brand bearings and regulator. So that pushed me to DIY!

So, this leaves the obvious choice- rebuild mine.

You have 2 or 3 choices in bearings. The economical choice would be VXB bearing.com which can sell you a front bearing (17X52X17) and a rear 6203 for about ~$20 + shipping. You can get the cheapest 6203 bearings are around a $1. You want ABEC 3 bearings which have a little extra clearance designed for electrical motors.

I decided to do hopefully better with purchase of bearings http://smithcoelectric.com/

Front Bosch replacement bearing is $39.95, rear I got a NTN for ~$6.

Brush/regulator I got a bosch from Autohaus az 1 197 311 213 for $27

Smith's also can sell you a new pulley ($38) or a replacement slip ring ($8.95) if yours is severally worn. Some times you'll need the plastic sleeve which fits the rear bearing(got to make sure you got it in the correct place on assembly!).

I knew the history of this alternator- it worked when removed. If yours is DOA, you should consider steps a little more carefully. Online, it appears that mainly failure of the diode packs is due to shorting of leads from jump starting or I guess you could experience this with a lower harness.

Disassembly:

Removed the main pulley (7/8 or 22 mm) with an impact wrench

Milwaukee cordless impact remove the 4 screws on the front. If you are not fully seated and straight- it WILL strip out the philips screw. Got 3 out of 4 removed. 4th, I drilled and tapped a Torx bit in to remove.

Rear of the alternator remove the next nuts for electrical wire attachments

remove rear cover- small hex or screws depending on model. Tabs pull out to allow removal of cover. Work it off with a screw driver or force.

remove regulator (2 #2 philips screws).

To make it easy- mark the housing halves.

Remove the 4 screws for the 2 halves. 8 mm works well.

Gently remove the back half. I put masking tape on the exposed wire to hopefully protect the coating. I cleaned and painted the exposed metal laminated plates.

Now for the rear bearing- I used a cheap-o Cumins small 3 jaw puller. I've ground down the threads to prevent it from damaging the slip ring which is plastic.

To remove the rotor from the front housing. I supported the housing with 2 pieces of 2X4 and hit the top dead blow hammer. I put the nut back on flange out- to provide a hitting surface.
One hand underneath to prevent it from hitting the floor and breaking the slip ring.

Now To remove the front from the shaft- I used a screw driver to work the space off first. Then I ground down the Pittsburg bearing puller ($1.99 harbor freight onside) to fit behind. If there is corrosion on your shaft- might want to
hit it with 400# prior to using the puller.


Slip ring replacement- pretty easy. Desolder wires @ the bottom. Pull/break of old ring, clean. Make a small pressing piece with 3/4 inch schedule 40 pipe and a pipe cap (PVC). Get the length right so you press on the end and the flange which is closest to the fan. There is a tab cutout in the fan so you clock the slip ring correctly. Press on and re-solder wires.


I'll update this with more pictures on re-assembly!


Michael

 

[nocfn]

Great writeup! When I got my car, I purchased a stock upgrade from 80a to 150a reman at BNR. Here is their link and I feel that they do great work at a fair price. Here is a link: http://www.ebay.com/itm/Mercedes-400E-500E-300SL-600SL-Alternator-W129-W124-Generator-/251920749547

 

[samiam44]

Thanks for the idea... but there are local rebuilders in every town. Problem is that use of ABEC 1 Chinese bearings. The only source for the front bearing non-import is BOSCH.

Got my order today- great parts service from Smith's. Both the Bosch bearing and the rear are NTN. Both are made in the USA!


I warmed the bearings in the oven(250F)- greased the bore lightly with synthetic grease and the mating shaft. They drop on and I seated them with a hammer tap on a socket. The small one, you can see I used the nut reversed to support the rotor. The large one, I used the socket.

Then add the spacer- the step goes toward the bearing.

Now it can functionally go back together, bench check or... I am going up the hill to a neighbor to bead blast the housings.

PS- I do great work too!

Michael

 

[Seangbadee]

Ok,

So I was looking for an option- I put a 143A out of a S500 in my car and it broke shortly after installation(new regulator and rear bearing installed). I got a second one and on inspection- no use putting it in the car. It has severe slip ring wear, both bearings are noisy. But I still had my original (120,000 miles) alternator which is 110A. Calling Tom Hanson @ classic center, looks like MB now wants $650ish for a factory rebuild. All the online stuff seems to indicate the black box Bosch (available at local auto stores) is rebuilt in Mexico with off-brand bearings and regulator. So that pushed me to DIY!

So, this leaves the obvious choice- rebuild mine.

You have 2 or 3 choices in bearings. The economical choice would be VXB bearing.com which can sell you a front bearing (17X52X17) and a rear 6203 for about ~$20 + shipping. You can get the cheapest 6203 bearings are around a $1. You want ABEC 3 bearings which have a little extra clearance designed for electrical motors.

I decided to do hopefully better with purchase of bearings Smith Co Electric - Alternators, Starters, & Service Parts

Front Bosch replacement bearing is $39.95, rear I got a NTN for ~$6.

Brush/regulator I got a bosch from Autohaus az 1 197 311 213 for $27

Smith's also can sell you a new pulley ($38) or a replacement slip ring ($8.95) if yours is severally worn. Some times you'll need the plastic sleeve which fits the rear bearing(got to make sure you got it in the correct place on assembly!).

I knew the history of this alternator- it worked when removed. If yours is DOA, you should consider steps a little more carefully. Online, it appears that mainly failure of the diode packs is due to shorting of leads from jump starting or I guess you could experience this with a lower harness.

Disassembly:

Removed the main pulley (7/8 or 22 mm) with an impact wrench

Milwaukee cordless impact remove the 4 screws on the front. If you are not fully seated and straight- it WILL strip out the philips screw. Got 3 out of 4 removed. 4th, I drilled and tapped a Torx bit in to remove.

Rear of the alternator remove the next nuts for electrical wire attachments

remove rear cover- small hex or screws depending on model. Tabs pull out to allow removal of cover. Work it off with a screw driver or force.

remove regulator (2 #2 philips screws).

To make it easy- mark the housing halves.

Remove the 4 screws for the 2 halves. 8 mm works well.

Gently remove the back half. I put masking tape on the exposed wire to hopefully protect the coating. I cleaned and painted the exposed metal laminated plates.

Now for the rear bearing- I used a cheap-o Cumins small 3 jaw puller. I've ground down the threads to prevent it from damaging the slip ring which is plastic.

To remove the rotor from the front housing. I supported the housing with 2 pieces of 2X4 and hit the top dead blow hammer. I put the nut back on flange out- to provide a hitting surface.
One hand underneath to prevent it from hitting the floor and breaking the slip ring.

Now To remove the front from the shaft- I used a screw driver to work the space off first. Then I ground down the Pittsburg bearing puller ($1.99 harbor freight onside) to fit behind. If there is corrosion on your shaft- might want to
hit it with 400# prior to using the puller.


Slip ring replacement- pretty easy. Desolder wires @ the bottom. Pull/break of old ring, clean. Make a small pressing piece with 3/4 inch schedule 40 pipe and a pipe cap (PVC). Get the length right so you press on the end and the flange which is closest to the fan. There is a tab cutout in the fan so you clock the slip ring correctly. Press on and re-solder wires.


I'll update this with more pictures on re-assembly!


Michael

I decided to open my 90 amp alternator in my 95 E320, and I'm certainly glad I did. Pine needles in the alternator, brushes worn, bearings almost bone dry and the plastic that the inner bearing sits in, was broken in 3 pieces.
I removed the front bearing from the housing using a gear puller, and then opened up the seal in front using a feeler guage and a precision flat head screwdriver. I was able to remove this seal without any damage at all.
When I was satisfied it was cleaned, I fed the bearings with MB bearing grease, worked the bearings, and then resealed. I did not remove the rear seal (front bearing) as there was no need to.
I did a similar cleaning for the rear bearing and both bearings are good to go.
I need to get a new plastic case sleeve, 4 new screws for the front (standard size m4.7 22mm), a new voltage regulator, and then I'll reinstall the alternator.

 

[Seangbadee]

The plastic 'case' is the tolerance ring!
MB calls it the slip ring

Slip Ring, Alternator 000-154-06-57 | MB OEM Parts

000-154-06-57 - Slip Ring, Alternator

www.mboemparts.com

 

[Seangbadee]

Help needed!
What are the torque numbers for the bolts that hold the alternator to it's bracket.
1995 E320.
Thanks