My alternator took a dump on me just as I was starting to tune the engine, so that just jumped to the top of my priority list.

I'm going to rebuild it, but I need a little confirmation on a couple things.

First off, Here's what I know for a fact needs replacement:

-Brushes are chipped, brush housing is cracked. Either wasn't assembled correctly at the reman place, or something got in the case while the car was on.
-Diode trio is bad. Can reverse bias all 3 leads to about 2300 ohms. Not all the way gone, but on it's way.
-voltage regulator. Not sure if it's bad or not, but it's a cheap generic one and I'd rather just replace it for the $10.
-Front and rear case bearing are bad. Can quiet them by lubing, but they were already making noise, meaning there was already metal on metal contact.

Here's what I don't remember.

I can reverse bias all 3 contacts on the rectifier, but it's something to the tune of 900 mega ohms. That should be fine, right? Or should I pay the $35 and get a new one?

The stator. It is normal to get a very low impedance reading between the 3 leads, right? Something like 0.2 ohms? The reading between the windings and field frame is open, like it should be.

Same thing with the rotor. I can get a very low reading between the slip rings, but an open reading between the rings and the pole pieces. This also correct?

If I use electrical component cleaner on the rotor and stator, will it remove the special varnish coating on the windings?

I have light oxidation buildup on the slip rings where the brushes contacted them. Can I use a fine grit sandpaper on them to clean em up?

Any other tips as I put it back together? None of the parts stores around here carry the parts I needed, so I had to special order from NAPA's warehouse. Should be here friday.



Thanks guys

 

Oh, and all the wiring is crappy and needs to be redone. I know the large one from the rectifier goes to the battery, but what about the other two?

IIRC, one goes to an ignition source, and the other one ties directly into the battery source, right?

It's a 3 wire off of my old 85 camaro, not the 4 wire that came stock on my 87.

 

Anyone?

 

The rectumfrier should check at .6 volts one way, whatever your meter reads (probably 600 ohms or so), and many many megohms the other way. All 6 diodes in it should read that individually. Frankly, if it's bad, it's new alt time; it costs more than the whole alt does.

You can clean up the stator with brake cleaner, diesel fuel, even lacquer thinner. The varnish on the wire is pretty tough.

The stator is 3 windings; each has a ring terminal at one end, with one common in the middle where all 3 are crimped / soldered together. Check that thing and make sure it's not developing bad connections.

Yes you can sand the slip rings lightly.

Your resistance readings are right.

The wire in the plug closer to the big termainl goes to the "Choke" light, and the other goes to somewhere that gives the regulator its sample of 12V to look at and attempt to control the alt output in order to hold the voltage at that point constant. If you hook the "Choke" light lead straight to ignition, you WILL fry the diode trio, because then under some circumstances, the alt will be trying to power everything on the ignition circuit, through the diode trio instead of the main recitfier; and the trio can't carry that much current without letting out its magic smoke. It's best not to attempt to rewire that part of the car, if you can find the original wiring, unhacked, back in the harness somewhere; just peel it back out of the split-loom until you get to unmolested factory wire, and get a new plug and extend the existing wires, and make sure you have a good "Choke" light bulb as the alt may never charge if the bulb is bad (because it won't "know" that the ignition is on).

The front bearing is a 6203. You can get it at any bearing place. It'll cost about a quarter as much from there as from an auto parts place. If you do that, get it with one side sealed and one side open; and install it with the sealed side toward the pulley. The rear bearing however is special, and very very very rarely needs replacement.

I assume you know about the special tool (J-21478-3Q, in the assembly manual) for holding the brushes back during assembly. There is actually a choice of 2 preferred tools: either a paper clip, or a toothpick. Hi-tech stuff.

 

That's some good stuff, so many ways to destroy that word

Thank you very much for taking the time to type out that response, you just put my mind at ease about the two most costly things in the whole alternator.

Even if I don't have a carbed car, should I still wire up the choke light as the charge indicator? Or will any light (circuit) work?

The main reason I ask is that my car is originally wired up for a 4 wire alternator, and I installed a 3 wire that I had sitting around. Both alternators are bad, but this one is the lesser of the two evils Not to mention the fact that it's all butched.

Oh, and I prefer the toothpick

 

Any light would work, but there's the issue of hacking into the wiring to find where it hooks up.

What I usually do, like when wiring up a boat or a street rod or something, is to use a 100 ohm 5 watt resistor between switched ignition and that terminal, to simulate the electrical effect of a light bulb.