27si alternator rebuild

[kraut83]

Recently put a new motor in my m1008, after getting it running discovered that my drivers side alt(gen1) isnt charging the battery. After some troubleshooting via the stickies I figured that the alternator was at fault and not the truck end wiring. I ordered a new alternator so this rebuild is for "fun". Worst case I dont get it fixed. Best case I have a spare isolated ground alt incase either of mine go out in the future.

I used the TM-34 to diagnose parts with in the alt. Along with the sticky info.
The diode trio tested out good, readings on one leg, no readings reversed.
the resistor is still reading 40ohms, figure its fine.
Tested the rectifier bridge, got good (500 on one side, OL on the other) for the positive end of the heat sink. On the negative side both tested OL. So bad Rectifier bridge.
The stator teste out with all 3 legs reading the same and nothing grounding to the body ring.
I almost stopped here figuring that the rotor shouldn't be bad, BUT for thoroughness I kept going with the TM instructions and tested the rotor as well. Testing the rings to shaft I got no continuity, good so far. However when testing the two rings against one another I got no resistance readings. I assume this means there is a broken wire/connection with in the rotor somewhere. I'm glad I didn't get a rebuild kit yet seeing that the most expensive part is bad.

Am I on the right path so far?
Does anyone out there had a spare rotor laying about?
Any other suggestions? other than "buy a new rotor and rectifier bridge".

 

[Keith_J]

Check where the slipring leads connect to the magnet wire through the claw pole half on the slipring side. There are two plastic insulators where the magnet wire goes through the claw pole half. Test the winding there, it could be the lead for the outboard slip ring where it goes under the inner ring.

Do you have a shop press? You can push the claw piece off and rewind the rotor. Might as well replace the slip rings. A rotor is under $60 complete.

 

[kraut83]

I have access to a press. Do i push the whole assembly off the shaft?
Im not sure what the part number is so the best Ive found for a whole rotor is 65.

 

[Keith_J]

https://www.steelsoldiers.com/showthread.php?128582-27SI-ROTOR-rewind

Remove the claw piece off the front or pulley end. Then unsolder the slip ring connections at the other claw pole insulators. Now slip the spool off and find the break. Rewind with the same gauge wire. If I recall correctly, it isn't potted or conformal coated, just wind tightly and secure with twine and varnish. Resolder the winding to slip ring connections and double check for continuity and no short to ground.

If you have failed rotor winding, chances are good the regulator and diode trio are also shot.

 

[kraut83]

Any suggestions on where to find one of these rotors? So far I've come up with nothing, one i managed to find is not a fit. And the other is asking over 100$ for one.

 

[Keith_J]

B07HHGC8ZX on that site named after a south American river. Cross ref numbers at site. 58-1/2 doll hairs US with free shipping if you paid for the frequent flyers program.

 

[kraut83]

Thank you very much sir!

 

[MarcusOReallyus]

B07HHGC8ZX on that site named after a south American river.

That would be Amazon.com. It's okay to say it. It's even okay to link to it. See? B07HHGC8ZX on Amazon.com


You can even say eBay! eBay! eBAY!!!! EBAY!


What you cannot do is to link to a live auction.

That's all. Mentioning other sites is perfectly fine. Even linking to a store front on eBay!

Just not a live auction.