Finally was nagged into replacing the wiring harness on my girlfriend's 82 242T today. While I was looking at the extent of the harness decay, I noticed that the alternator (the original 55amp) was starting to squeal and she mentioned some strange electrical issues that could have either been attributed to a bad ground (harness) or a failing alternator.

So I took an alternator I had from an 89 or so 240 and had it rebuilt (now 90 amp) and planned on putting it into the turbo. The same guy has rebuilt 2 other alternators for me with good luck so far. I had forgotten about the extra post/nut on some of the newer alternators. Since my 86 is in the shop for a smog and I can't compare the wiring on that (I seem to remember it has an extra post), can anybody advise how to wire this now?

B+ (10mm nut) gets the big red wire
D+ (spade) gets the little red wire
Ground (8mm nut on the edge of the housing) gets the blue ground wire

What should I do with the extra post that seems to be equidistant to the D+ stamp on the housing (another 10mm nut)? I left it unhooked and the moment everything was wired back up, I got the alternator failure light on the dash and no charge.

I double-checked all other ground points and connections for the new harness and it is a clean OEM replacement harness (dark grey connector). Car turns over fine and runs better than before, just no charge.

I will enjoy a frosty cold beverage in hope of enlightenment. Thanx.

The D+ is a spade on some alternators, and a post on others. The post type can be adapted to a spade type (check the coil primary terminals to see what I mean).

I think you put the small red wire on an unused terminal meant for a filter capacitor. I looked at an 80A core I have, and that filter spade treminal is "equidistant to the D+ stamp on the housing". (This is how the 80A alternator is configured.)

If I'm right, you will either need to put an "eye" terminal on your red wire, or adapt the post for the red wire's spade terminal. Also, the post takes an 8mm nut.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Your post was exactly right. After taking some readings across each post, turns out the smaller post was the D+. So I just changed the wire and all is good. Thanks.

Here's a side-by-side comparison. Old alt on left, new on right. Any thoughts appreciated. Only weird thing is that between the second post and the spade connector is stamped the D+. Wonder if I should just hook up the B+ on that unknown pole.