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  #1  
Old 02-23-2013, 08:30 PM
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Installing An Upgraded 80 Amp Alternator And 9-Blade Fan In A 1980 W116 300SD

This post is about upgrading my 1980 W116 300SD to an 80 amp AL69X alternator and 9-blade fan with smaller pulley. Similar principles may apply in other chassis and models of Mercedes. Installing a 115 amp AL129X alternator should be the same procedure.

Since funds are currently very limited, I went around to the wrecking yards looking for alternators. The only vehicles with nice alternators had different wire connections than mine, except for old, nasty 55 amp ones like I had. I saw a couple nearly new Bosch Premium remanufactured 80 amp ones on two W126s, but unfortunately they were the kind that don't fit my car.

After going home and thinking about it, I decided I would make one of the AL69X 80 amp alternators fit. If I was successful, it would allow me to upgrade to a 115 amp AL129X in the future, if needed.

When I went back to the yard, I pulled both 80 amp alternators, which looked equally nice, and compared the two to see which was in the best condition. I was able to loosen the pulley nut one one, but the nut on the other one was so tight that the 8mm hex key socket spun inside the shaft, so that helped me decide which to purchase.

I also found a 9-blade fan and small fan pulley in a 1983 W126 300SD. The plastic 9-blade fan is lighter than the 6-blade magnesium one, and is supposed to take less force to spin, therefore will slightly increase fuel mileage. The extra blades increase air flow, and the smaller pulley spins faster, therefore causing the fan and water pump to turn faster.

The first thing to do is disconnect the negative battery cable to prevent sparks, component damage, and electrocution.


Then the two 17mm bolts and nut are loosened at the rear of the alternator.


Then loosen the belts by turning the 13mm tension nut counterclockwise.


I got tired of rounding out fan bolts, so I ground the end of my 10mm wrench so that the box end will fit over them.


Next, the fan and pulley are removed.


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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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  #2  
Old 02-23-2013, 08:31 PM
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Here is my old alternator with the shiny new voltage regulator that did no good.


The old alternator dropped out the bottom with the adjuster bracket still attached.


The bracket and bolt were bent from people in the past not having all the nuts and bolts loose before adjusting the belt tension.


The 80 amp alternator is on the left, and the old 55 amp alternator is on the right. The body and hole spacing of the 80 amp alternator is slightly bigger than the 55 amp version. The electrical connections and voltage regulator are also in different positions between the types.


They are close to the same depth, but the 80 amp one is a little deeper.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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  #3  
Old 02-23-2013, 08:31 PM
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I removed the 80 amp alternator from a W126 V8 car, so it has only a single belt pulley. Mine uses a double belt pulley, so I had to swap them out. It's not the best way, but I was able to remove the nut on the 55 amp alternator by wedging screwdrivers between the fan and body.


The nut on the 80 amp alternator was easier because the shaft has a spot to insert an 8mm hex key socket. I didn't have a socket or wrench large enough to fit on this larger nut (larger than 23mm, smaller than 27mm), so I was forced to use an adjustable wrench. The 80 amp alternator lacks the Woodruff key and relies on tightening force of the pulley nut.


I was able to fix the positioning of the electrical connections and voltage regulator by removing the four screws that hold the two case halves together, loosening the ones at the front bearing behind the pulley area, then rotating the case halves 180 degrees. You have to press down hard on the screws and be extra careful so they don't round out when you turn the screwdriver/socket when loosening.



I decided to do a test fit of the 80 amp alternator, 9-blade fan, and pulley. The 10X1035 belts I was using were very loose even with the tension screw fully tightened (due to using a smaller fan pulley). I loosened the power steering pump and removed the belt in order to test a smaller, 10X1000 fan belt I removed from a 1983 300SD, from which the 9-blade fan and small pulley came.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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  #4  
Old 02-23-2013, 08:32 PM
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I tried the 10X1000 belt, but the tension screw wouldn't loosen fully. Because the 80 amp alternator is larger, the adjuster bracket was at a steeper angle and was hitting the screw side of the hose clamp on the water pump housing above it. By the way, Kobalt Tools (found exclusively in Lowe's home improvement stores) has a handy double drive ratchet that allows you to twist the handle in either direction to spin the socket below, and works great for this job.


I rotated the screw side of the hose clamp away from the bracket, and this gained additional clearance, but the adjuster bracket was soon hitting the hose.


I ended up having to take a rotary tool with a cutoff wheel and grind away almost all the way up to where the indentation in the bracket starts. This worked and the adjuster bracket cleared the hose above it. There was now just enough room that I was able to stretch the 10X1000 belt onto the pulleys.


Since the 80 amp alternator has different electrical connections, I had to rewire my car. The 80 amp alternators need thicker wiring than the 55 amp ones and might fry the stock wiring. The square alternator plug has two red wires which go to the junction block under the battery. There is a third, small blue wire that runs up to the charging light in the instrument panel. A red/black wire from the temperature sensor on the top of the water pump housing enters the same harness. It's a good idea to unplug the connector at the sensor before working on this because when the alternator is lowered, it tends to catch on the wire.


The two red wires coming from the rectangular alternator plug go directly to the junction block under the battery, BUT a little bit of them is tucked into the sheathing of a nearby wire harness. They will come out if you carefully and patiently pull on them. I will say that this is really difficult to do from under the car... it would be easier to access these wires with the battery and tray out, but I didn't want to remove them.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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  #5  
Old 02-23-2013, 08:33 PM
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I removed the alternator wire harness from the W126. There are two different lengths, depending on the year. I think the first generation W126s have the shorter version (which is needed in this application). It's part number 126 540 04 08 for those interested (apparently a $50 dealer part).


Since on the W116 the blue charging light wire does not connect to the junction block, but goes directly to the instrument panel light, the end of the blue wire on the harness needs to be attached to it with a connector. Make sure you do only the side that does not attach to the alternator since the red wire has a larger connector on the alternator side.


I took a razor and carefully cut away the sheathing on the alternator harness, being careful to not cut into any of the wires (especially the red/black one for the temperature sensor). If you cut most of the way, but not completely through the sheathing, most of the time you can pull it apart.


Once the sheathing is off, you'll have exposed wires. The factory did a dirty trick and made one of the two red wires from the alternator harness use the same connector as the wire that goes from the junction block to the wire harness that goes up the inner fender. So, I cut the red wire on the alternator side where it bends and gets tucked into the sheathing. After cutting it, I put electrical tape over the cut end and tucked it back inside the sheathing of the wire harness that goes up the inner fender.


I attached the connector on the small blue wire, and installed the red wire of the new alternator harness to the lower connection on the junction block since it would not fit on the middle connection because of the thickness of the connector. The middle and lower connections on the junction block are linked together, anyway. I made sure to sand the connections and used dielectric grease on them.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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Old 02-23-2013, 08:33 PM
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Here is the W126 alternator wire harness installed.


I sanded the belt surface of the small pulley with 80 grit sandpaper, making perpendicular lines to discourage belt slippage.


The old 6-blade fan and large pulley are on the left, and the upgrade 9-blade fan and small pulley are on the right.


Here is the pretty 80 amp alternator ready to install.


The body of the alternator is supposed to be grounded to the bracket, which is grounded to the engine block, which is grounded to the body through a strap. I sanded and used dielectric grease wherever the alternator touches the bracket.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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  #7  
Old 02-23-2013, 08:34 PM
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I straightened and painted the alternator adjuster bracket and bolt.


The adjuster brackets were plated at the factory, so since I painted mine, I scratched away the paint where the alternator contacts it, and where the adjuster bracket contacts the bracket, in order to better ground it (dielectric grease was used on these points).


I installed the alternator and adjuster bracket, loosening the tension screw as far as it would go. I couldn't get the new 10X1000 belts I ordered to fit on the pulleys. I realized this is because the new belts weren't stretched out yet, therefore would not go on. There was still room for the tension screw to move, but the body of the alternator was preventing it from moving any further.


I tried all kinds of ways to get the belts to fit, but I could not get one on the inner track of the pulleys. There was enough room to get used, stretched belts on, but not new ones.


The only way I could get the new belts on was by removing the fan and pulley, putting the belts on with the pulley, screwing in one fan bolt a few turns, and sliding on the fan and installing the other three bolts. 10X1035 is too long, and 10X1000 is too short. Ideally, I need an in-between belt size.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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Old 02-23-2013, 08:35 PM
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Here is the alternator installed with a boot I removed from a W124.


The 9 blade fan and small pulley are installed.


My upgraded alternator is in place with new (albeit slightly too short) belts. There is more travel room on the adjuster bracket to loosen the tension screw, but the alternator body hits the lower bracket. Once the belts were in place, they were fairly loose and tightened up just fine.


I put a multimeter on my battery and it showed a 13.08 volt charge.


With the engine at idle, the voltage started climbing, showing that the alternator is working and is charging the battery.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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Old 02-23-2013, 08:48 PM
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good grief your car is impeccably clean, Kudos to keeping it that way. love reading your writeups despite not owning a SD anymore or a W116
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Old 02-23-2013, 10:56 PM
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X2000000000 on the clean vehicle! wow.
you'd have had an easier time with the alternator if you'd gotten the small pulley from the alternator you got the fan from... it's about 3/4" smaller diameter.
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Old 02-24-2013, 12:35 AM
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Quote:
Originally Posted by vstech View Post
X2000000000 on the clean vehicle! wow.
you'd have had an easier time with the alternator if you'd gotten the small pulley from the alternator you got the fan from... it's about 3/4" smaller diameter.
Ah man, I didn't know about that! I'll have to keep a look out for one. It will also make the alternator spin faster and charge more at idle.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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Old 02-25-2013, 01:08 AM
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617.952

Which version of the 617 engine is in your 300sd? I see in the pictures the dual oil drain/return lines, and the oil/vapor seperator in the air cleaner.

The reason I ask, is I am replacing the original .950 engine (#5 cylinder died a noisy death, knock, then blew the tip off the prechamber) with a .952 engine. I have read conflicting stories on wether it will fit around the cross body stiffeners and supports.

I like your alternator bracket modification to get it to work with the larger alt.

Hammerwerfer
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Old 02-25-2013, 02:51 AM
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Quote:
Originally Posted by HammerWerfer View Post
Which version of the 617 engine is in your 300sd? I see in the pictures the dual oil drain/return lines, and the oil/vapor seperator in the air cleaner.

The reason I ask, is I am replacing the original .950 engine (#5 cylinder died a noisy death, knock, then blew the tip off the prechamber) with a .952 engine. I have read conflicting stories on wether it will fit around the cross body stiffeners and supports.

I like your alternator bracket modification to get it to work with the larger alt.

Hammerwerfer
I believe I have the .951 engine. I'm not sure if the .952 engine upper oil pan fits in the W116 body or not, though I've heard it doesn't clear.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles
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Old 02-25-2013, 03:35 AM
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thanks

.

as I have 80A left over after V8 engine swap
this is a topic I was waiting for!

thanks mate!


.

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