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

Squiggle Dog · #5 02-23-2013, 08:33 PM

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.