Resolved 1G Alternator posts

[greekgodchaos]

My new (top) alternator showed up but it has 2 posts, my old one had 1. Are they both going to the battery or is one ground? I was having a non-charging issue with the one below so I got a Galant 90 amp version to replace it.

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Additionally, the alternator on the bottom, where the top stud should be is grounded, the new one is the opposite. Where the lower stud is grounded but the top one is not.

I have a few old dead OEM alternators I compared it to and this one I am replacing seems like an odd duck, as all the others have the B+ post in the top-forward position and where the bottom posts are on these 2 pictured, there isn't any on the OEM ones. It's just an open threaded hole.

 

[luv2rallye]

On all alt's the post that is insulated is B+ (goes to battery positive). The alt casing is always ground and is usually connected to battery negative through its mounting to the engine/frame. Some alts also have a negative post to connect a cable to ground should one want this or because the alt mounting doesn't connect to ground so you would then need it (notice this post is bolted to the alt casing). The location on the alt of this negative post makes no difference, it's just where the manufacturer put it.

 

[greekgodchaos]

I'm still confused on why the design is different and why the one I am removing has the B on the bottom instead of on top like all the others I have do. Bad luck of the reman draw I suppose? I already had a supplemental ground wire going to the frame from the rear pivot bolt so I might just put a rubber cap on the bottom ground post.

 

[steve]

As you note these are two different alternators. My 91 looked like the top version.
While you can use the second post to ground the alternator I believe it was used to secure the cable harness so it didn't bounce around from the factory.

 

[19Eclipse90]

I have the (2) white wires attached to the post “above” (as-viewed, when mounted) the 2-pin connector on my 90A Galant alternator.

From the top:

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From underneath:

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And I actually had shorting issues trying to attach it elsewhere. Blew through 2-3 alternator fuses before I figured out what was happening.

 

[greekgodchaos]

A big thank you to everyone for your input. I went ahead and attached the wires going to the fuse on the upper stud and I am now getting the 14v I wasn't getting before.

 

[steve]

Here's the diagram from the FSM for reference. You'll note it looks like the top one.

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