PeachParts Mercedes-Benz Forum - View Single Post - Installing An Upgraded 80 Amp Alternator And 9-Blade Fan In A 1980 W116 300SD

Squiggle Dog · #4 02-23-2013, 08:32 PM

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.