ALTERNATOR REPLACEMENT w123 - PeachParts Mercedes-Benz Forum

BenzBid · #1 09-30-2010, 11:28 AM

Anyone got a .pdf or a link to a DIY alternator replacement? I have found a few step by steps here on the forum, but nothing with pictures and or drawings.

If someone can send or point me to a link that would be very kind.

Thank you!

Fattyman · #2 09-30-2010, 11:45 AM

No link but I'll try to talk you through it. Disconnect the battery ground. Unplug the wire at the alternator. One 17 mm bolt attaches the tension bracket to the motor (remove first, right under the thermostat housing) You'll need a flex head ratchet to make it easy. One 17 mm bolt attaches the alternator to the motor on the bottom (you'll have to go under the car and remove second). The alternator will now hit you in the head! I have described the most direct way of doing it as I know others will chime in. This way the tension bracket will come out with the alternator under the car. You can do it without removing the bracket from the car as well. I think you need to see for yourself how the bracket attaches to the alternator though. Simple yet hard to describe. Remove the 17mm bolt on the back of the tension assembly BEFORE you turn the 13mm tension bolt. I hope this helps.

tangofox007 · #3 09-30-2010, 12:14 PM

Quote:

Originally Posted by Fattyman

You can do it without removing the bracket from the car as well.

Not without bending some metal.

Quote:

Originally Posted by Fattyman

Remove the 17mm bolt on the back of the tension assembly BEFORE you turn the 13mm tension bolt.

I think you mean "Loosen the nut on the back of the bolt." The bolt runs front to rear and cannot be removed until the tensioner is fully run out, which cannot happen until the tension bracket is removed from the mounting bracket.

Fattyman · #4 09-30-2010, 02:33 PM

Correct, I meant nut, not bolt. Thanks.
The bracket can stay on the car without damage to remove the alternator. I've done it many times to save the trouble of backing out the bolt on the block. The tension bolt can also be removed from the bracket while still on the car. Just spin it clockwise and it comes out underneath the fan belt. Mounting the alt back onto it can be a pita for someone who hasn't done it before. Lining up the bushing etc.. Hence the suggestion of leaving it on the alternator so the owner could see how it looks.

tangofox007 · #5 09-30-2010, 02:44 PM

Quote:

Originally Posted by Fattyman

The bracket can stay on the car without damage to remove the alternator.

On the vehicles that I have dealt with, the alternator will not move far enough remove the adjusting rod from the adjusting nut with the bracket installed. (Movement of the alternator is physically blocked before it can get to the end of the track.) There are likely a few cars out there in which someone had cut a few mm off the rod to avoid the problem of having to remove the bracket. Or maybe not all adjusting rods were of the same length to start with.

Bottom line: If you cannot run the adjusting rod out of the nut, remove the bracket. If you don't want to have to remove the bracket next time, cut 5/16" off the threaded rod.

Fattyman · #6 09-30-2010, 05:07 PM

I forgot. One more thing. You should loosen the tension on the belts first or it will be a pita no matter which way you do it! Have Fun

toomany MBZ · #7 09-30-2010, 05:32 PM

I had to remove the bracket bolted to the engine block, as one of the bolts was unable to come completely out. Yours my be different.

Fattyman · #8 09-30-2010, 05:52 PM

Ah yes, these cars develop a personality of their own as time goes by. If the bolt that holds the adjusting bracket to the engine is too tight to turn by hand I leave the bracket attached to the motor. If it turns freely I remove it with the alternator. To make things more festive there are 2 types of brackets used with the later style tension bolt. One has a rectangular cutout and one does not. You cannot use the cutout style on the larger Bosch AL129X alternator as it will interfere with the heater hose outlet. You also have to turn in the tension nut so you can get the bracket back on the engine block. The AL129X alternator is physically larger and will hit the motor otherwise.

funola · #9 12-23-2010, 10:25 PM

Quote:

Originally Posted by Fattyman

Ah yes, these cars develop a personality of their own as time goes by. If the bolt that holds the adjusting bracket to the engine is too tight to turn by hand I leave the bracket attached to the motor. If it turns freely I remove it with the alternator. To make things more festive there are 2 types of brackets used with the later style tension bolt. One has a rectangular cutout and one does not. You cannot use the cutout style on the larger Bosch AL129X alternator as it will interfere with the heater hose outlet. You also have to turn in the tension nut so you can get the bracket back on the engine block. The AL129X alternator is physically larger and will hit the motor otherwise.

Do you have a pic of the bracket that works with the larger AL129X? I am about to put this alternator into my 83 300D turbo.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=170574879052&viewitem=&sspagename=STRK%3AMEWNX%3AIT

Will my 83 have a compatible bracket to the Ebay alternator?

Fattyman · #10 12-23-2010, 10:56 PM

That alternator will work but but it does not come with a pulley. They tell you you will have to use your pulley which being the stock size will make the install a little more festive. Meaning that you may have to thread your belts onto it first before you mount the bracket to the block. This depends on what belts you have. I run a smaller pulley which allows you to run the stock size belts. It also spins the alternator faster at idle so you get a full charge rate even while sitting in traffic with all your goodies turned on. If your bracket does not have a stamped out square opening it will work with that alternator. I'm sorry, I don't have a pic. You also want to make sure that the wire mounting studs are on the opposite side of the alternator mounting ears. That will put them on the passenger side of the car when the alternator is mounted and your wiring harness will be able to reach them no problem. If the studs are not in that position your harness may not reach and they also might be blocked by the AC hoses. The picture on the ebay ad does not look like the studs are mounted in the right spot. You can split the alternator and put them where you want but they may void your warranty.

funola · #11 12-23-2010, 11:07 PM

The Ebay seller emailed me that he included a double pulley. Hoping everything will go in smoothly.

Fattyman · #12 12-23-2010, 11:26 PM

Ask him how he positions the mounting studs for your wires.

funola · #13 12-23-2010, 11:40 PM

The alternator is suppose to arrive tomorrow. I'll see how the terminals are positioned then.
Any tricks getting a wrench on the top alternator bolt? As I recall, the water pump pulley was in the way.

vstech · #14 12-23-2010, 11:44 PM

Quote:

Originally Posted by funola

The alternator is suppose to arrive tomorrow. I'll see how the terminals are positioned then.
Any tricks getting a wrench on the top alternator bolt? As I recall, the water pump pulley was in the way.

the top bolt should not need access from behind the WP pulley. that nut should be welded to the frame... all bolts should be loosened from the back side of the alternator.

Fattyman · #15 12-23-2010, 11:49 PM

The bolt that holds the bracket to the block is facing the firewall. Use a long flex ratchet with a 17 mm. The bottom bolt is the same animal but a ratcheting wrench is a better choice down there. Do the top one first. Undo the wires. Go under and do the other bolt and it will drop down with the bracket still attached. You may want to slack the belt tension before going under.