M1028 Alternator Rebuild Questions

[Warthog]

Just use what is in the bearing. If you get too much it will spread inside the alternator

 

[Corvette1974]

Just use what is in the bearing. If you get too much it will spread inside the alternator

Alright sounds good. Tomorrow the Alts will be done and I'm also putting new Energy Suspension sway bar bushings in and new Monroe gas magnum shocks and steering stabilizer. This truck is gonna be set once I'm done with it!

Will

 

[parlay100]

No you good to go as is. The rear is a needle and will just spin out any extra. Be sure to support the rear housing really well. The rear tends to crack in the same spot on the flat piece next to the bearing housing if not supported. Let me know if you need any help. i will walk you through it.

 

[Corvette1974]

No you good to go as is. The rear is a needle and will just spin out any extra. Be sure to support the rear housing really well. The rear tends to crack in the same spot on the flat piece next to the bearing housing if not supported. Let me know if you need any help. i will walk you through it.

I have been using a large socket to go around the place that holds the bearing in when I punched it out. I will do the same when I install it. Should I put a light oil on the bearing outside to ease it in?

Will

 

[Warthog]

I defer the knowledge award to Parlay100 as he does this for a living. I just do it out of neccessity.

No need. It is a tight fit but it will slide in easily.

Don't get in a hurry and DO NOT FORGET the backup support.

 

[parlay100]

Yes I forgot to mention that, oil will help.--but not needed We use a socket and a arbor press.

 

[Corvette1974]

Yes I forgot to mention that, oil will help.--but not needed We use a socket and a arbor press.

Ok I'll see what I can do. I have a questions though. I tested both alternator stators and they check out (continuity between the three tabs but not to the case). I checked the rotors though, and I get differing values. The driver side rotor has continuity between the two slip rings, but not between them and the shaft (this is good?). Tha passenger side, however, has no continuity between the two slip rings, and no continuity between the rings and the shaft. What is the deal here is the rotor bad? I will point out that Alt 2 (passenger) was not working, which is why I got into rebuilding that alts in the first place. Do I have a problem here?

Will

Edit: I checked the TM again and like I remembered, it doesnt say anything about testing the rotor, just cleaning it. It does say to test the stator, and both of mine passed.

 

[Corvette1974]

Any ideas as to if my rotors are good or not?

Will

 

[Warthog]

You need continuity between the two slip rings. The one without is bad. It may be repairable. You may need to get a new/used from an alternator shop.

The shaft needs to be isolated from the rings.

 

[Corvette1974]

You need continuity between the two slip rings. The one without is bad. It may be repairable. You may need to get a new/used from an alternator shop.

The shaft needs to be isolated from the rings.

Hmmm ok there is no continuity on either between the rings and the shaft (this is good). One has cont. between rings, the other (the alt that wasnt working) does not. Is there any way I can test the actual windings and bypass the possibly faulty slip rings? Would you think it is an internal problem with the windings or just the slip rings? Could it be just bad solder joint on the ring wires? And I have seen new slip rings for sale, could I install a new set if these are somehow bad?

Sorry 'bout the number of questions, I just am trying to get to the bottom of this so I can drive my truck!

Thanks,
Will

 

[Warthog]

They do sell replacement slip rings. It could be as simple as a bad solder joint.

Here is a place that sells parts. You can get an idea of what to look for.

Alternator Parts - Starter Parts - Alternator & Starter Repair kits - GM Delco

The alternators are GM 27SI type 100 units.

Start at the rings and work back to the windings to find a break in the wire.

Think of the windings as one loooong wire. One end starts at one of the slip rings, winds thru the rotor and exits out the other ring.

Any break in the wire causes the circuit to fail

 

[Corvette1974]

They do sell replacement slip rings. It could be as simple as a bad solder joint.

Here is a place that sells parts. You can get an idea of what to look for.

Alternator Parts - Starter Parts - Alternator & Starter Repair kits - GM Delco

The alternators are GM 27SI type 100 units.

Start are the rings and work back to the windings to find a break in the wire.

Ok. A few things. Is it ok to unsolder the slip ring wires from the "connectors" on the frame of the rotor, this wont damage the insulation/varnish or anything? But I shouldnt need to unsolder it. Couldnt I just clean off the varnish on the frame solder "connector" and check it there and if this doesnt have continuity then there is a problem with the windings?

What I'm trying to get at is that slip rings arent real technological. They are just metal and wires. But either way, Let me check the windings directly and report back.

Will

 

[Warthog]

No need to unsolder unless you are replacing the rings. Just clean the solder connection and check the resistance.

All the rings are are two copper rings with wire leads attached to them.

The alternator shops replace them all the time is needed.

 

[Corvette1974]

Should there be absolutely no bubbles or "melting" in the varnish on the windings? There is no obvious burning, but there is definitely an area with some not perfect looking varnish. Could this indicate a bad winding? But wouldnt if the winding fail it would still have continuity, it would just be a short?


I also cleaned off the connector tabs and tested it there. Still nothing...

Will

 

[Corvette1974]

No need to unsolder unless you are replacing the rings. Just clean the solder connection and check the resistance.

All the rings are are two copper rings with wire leads attached to them.

The alternator shops replace them all the time is needed.

How do I clean the solder connection without unsoldering? Also I connected the slip rings together and checked from one slip ring wire to the other and it read good, so the slip rings themselves are good.... So what can I do now? Is there any way to test just the windings?

Will

 

[Warthog]

Maybe time for a new rotor.

I had one that had a break deep inside the winding. It happened when part of the rotor broke off...... lol

You should be able to get one at an alternator shop.

Or you could buy on of the Autozone units and swap out the rotor. Just a thought

 

[Warthog]

Clean the solder joint with a small file. Expose the clean solder and check it.

 

[Corvette1974]

Maybe time for a new rotor.

I had one that had a break deep inside the winding. It happened when part of the rotor broke off...... lol

You should be able to get one at an alternator shop.

Or you could buy on of the Autozone units and swap out the rotor. Just a thought

Clean the solder joint with a small file. Expose the clean solder and check it.

Ok I did clean off the joints then. It reads good when I connected the slip rings together (thus creating a circuit) but when they are not connected, nothing.

If this is a bad rotor, I'll see if I can get a replacement. On that website you said before, they have new rotors, but only for the 27SI Type 200, not the type 100 you said our alternators are. Is this correct? I just need to know in case it was a typo or something lol.

Do you think any alternator shop will have rotors for the alternator just lying around?

Will

 

[Warthog]

Call the shop and ask them.

The CUCVs use the type 100 units

My local alternator shop had dozens of them laying around.

 

[Corvette1974]

Call the shop and ask them.

The CUCVs use the type 100 units

My local alternator shop had dozens of them laying around.

Haha ok sounds good. I'll look into that tomorrow.

Is there any reason that this rotor failed? The other one is perfectly fine. They both are the original military issue units.

Will