1985 442 78 Amp 12SI Alternator Restoration

[69hurstolds]

Found them. Bought them from Mouser Electronics sometime last year. They're a little bit more off-white than the originals. And although they are semi-transparent, not as much as the factory deals. I hadn't seen them in a bit and thought they were more transparent than they really are, but I imagine they're more like the pigtail that Delco has been packaging. The A/C compressor plug connectors in the same box.

There is a molded in number on the end of the tab face, typically the mold number, as well as "PED" on the back like the factory plug. The terminal ports where their inserted also has and A and B molded in on the end edge of the ports. Just like the originals as well.

 

[69hurstolds]

Did all the electrical resistance checks on the new components. No sense putting in stuff that's junk. Everything checks out within specs per the CSM testing procedures. I'll double check them again as they get installed.

 

[69hurstolds]

Finally got the alternator broke down and disassembled. Got set back about a half hour because of a dead battery on my impact. So after a while of charging, wearing leather gloves, I grabbed the fan and held it tight, then it took 2 ugga uggas and zip, off the pulley nut came. You really need an impact wrench to remove the shaft nut without risk of breaking the alternator somehow or your fingers/arm. It's only like 50 lbs./ft of torque, but that wave lock washer is a mother bear on tension. Impact wrench makes it super easy.

Kinda dirty inside due to brush dust, but that's expected. 60K miles on it. Ironically, the original rotor and stator checked out EXACTLY the same as the new rotor and stator resistance and open checks. The diode had a bit more resistance in it than the new one, and so did the rectifier. Rectifier was creeping up on some of the readings over 5 and a half ohms. Nothing serious, but run time, heat, and age obviously has a slight effect on the rectifier and diode.

Diode had a mfr date of 5A29, or Jan. 29, 1985. The rotor also had a stamp of 5A466. Meaning those codes ARE manufacture dates. This was January 85, with the 466 last 3 of the part number. Interestingly, the new rotor is date stamped 4G466. (July 84).

 

[69hurstolds]

So for funsies, I was looking at a few alternator videos by people I believe know wtf they're doing. One video had an experienced electrician redoing an alternator. In it, he had some recommendations that seemed to make sense. At least to me.

One of the deals was that he said since most stators have naked terminals, ACDelco stators no exception, and they come EVER SO CLOSE to the rectifier fins, which are grounded, one wrong bend and one or more of the stator wires are touching the rectifier and grounding out. He said use a couple wraps of 3M Super 88 tape, since it is thicker, has better heat resistance, and unless you have some super shrinkable heat shrink tubing, it will do the job. He swears by it.

Here's a 10SI single wire alternator showing the stator terminals attached to the rectifier (circled in yellow). It's very similar to the 12SI. The stator connector wires end up very close to the rectifier bridge which is grounded. It would suck to do all that work and short out your alternator.

So this is what I used. The goal isn't to make a water/air tight seal. Grounding protection only. Just stretch it slightly while wrapping and it will make a perfect anti-grounding boot near the terminal end.

Another tip that made sense to me is the brush wire positions. It's free, costs nothing but about 2 seconds of time to extend brush life. When the brush assembly is in the box, it may come to you where the wiring is bowed toward the slip rings on the alternator. While it's not an issue when the brushes are new and long, over time the brushes wear, and the wires can move forward toward the slip rings. And eventually they could possibly touch the slip rings, wear through and stop the power generation.

As you can see here, this is how MOST of the brush holders come from the vendors who sell them. Left and Right sides are the same. ACDelco, in this instance, was no different. Note the position of the brush wire. As the brush wears against the slip rings, the wires would move closer and closer to the slip rings, possibly touching the rings depending on how bad the brush wear was, and wear through. Not a good situation. The brush blocks are supposed to be the wear items, not the wire.

As you can see below, it just takes the end of a pen and gently bend the wire back the other way. This way, as the brush wears, the wire should never come in contact with the slip rings.
Others on this forum can tell you, the devil's in the details. A little extra time and care and you're golden and get more life out of your alternator.

The only real torque setting you need to remember is that the pulley nut is 40-60 lbs/ft. The rest of the screws should be fully seated snugly and not stripped. That's it for now. Gotta wait until I get the housings back.

 

[Rocknrod]

Great information as usual. So will you be posting a pic of the stator terminals wrapped and installed for informational purposes?

 

[69hurstolds]

Great information as usual. So will you be posting a pic of the stator terminals wrapped and installed for informational purposes?

In due time. After the place I'm sending the casing halves out to have refinished gets them done and back to me then I can start reassembling the junk.

I put the stator back in the pile of parts, so I didn't take a picture of it. Not much to write home about. Just taping up the wire and terminal lug stem.

 

[Rocknrod]

Well is it like using heat shrink on a ring terminal? Only using tape?

 

[69hurstolds]

As I said, you could use shrink wrap if you like. But you'd have to ensure it was able to go over the terminal and shrink down ratio was enough to stay in place. Terminals are already installed, making it a bit tougher to use shrink wrap. That's why taping it is a sure thing. The only real reason for it is for ground protection, nothing else. It's not like it's a major operation or even required. It's just a tip of something you can do to help prevent accidently grounding the stator windings.

 

[CopperNick]

There is a version of electrical tape that will bond permanently to itself. The instructions indicated that once you wound the tape around the wires you had about twenty-four hours before the bond between the layers of tape became perrmanent. At that point the only way to remove it would be to get out an Olfa knife and start cutting. Think I still have part of a roll of that stuff still around but have to find a vendor locally that carries it as that roll has gone awol.



Nick

 

[69hurstolds]

There is a version of electrical tape that will bond permanently to itself. The instructions indicated that once you wound the tape around the wires you had about twenty-four hours before the bond between the layers of tape became perrmanent. At that point the only way to remove it would be to get out an Olfa knife and start cutting. Think I still have part of a roll of that stuff still around but have to find a vendor locally that carries it as that roll has gone awol.



Nick

It's called Scotch 23. You could use that too. The point is, the idea is to insulate the wiring because of the close proximity to the grounded fins of the rectifier. Your roll of the self-welding tape must've got up with mine and ran off together. I can't find my roll either. That stuff ain't cheap like the 88. But the Super 88 tape should do just fine since intake air will be flowing across it when it's running anyway. All the electrician guys at work used it.