27SI ROTOR rewind?

Keith_J

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It finally hit me, an alternator that a repair kit couldn't fix. Since I couldn't find a replacement rotor and the vehicle is a daily driver for the youngest son, I broke down and bought an autozone non isolated ground. It I'd for the left side position, working fine now.

looking over the rotor, it appears to be easily rebuildable. Just push the shaft off one of the claw poles, then desolder the two leads. Unwrap the old spool, weigh the copper and replace with same gauge and weight.

resolder and push back together.
 

rtk

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Is that ROTOR any different than a normal GM ? I seem to remember rotors and stators were the same except for AMP output . I know about the isolated ground issue , but maybe you could find a junk alternator of the right output and use that for your rebuild . Then just use a rebuild kit for the internals . Bob k
 

Keith_J

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I went to the local rebuilder, they only had series 200 type 27SI rotors. But at $128, the Autozone alternator was cheaper and right now.

It LOOKS rebuildable, the drive end claw pole is pressed onto the shaft over splines, there are two holes which could be tapped to hold that pole piece while the shaft is pushed out. Once that is done, then the coil disconnected by melting the braze points. Rewinding the spool is not an issue at all.

My supplier doesn't seem to have them, I will check with the Delco Remy part number. Still, I think the wire would be cheaper. The slip rings are in fine shape.
 

eme411

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do not waste your time rebuilding the rotor these can be had new or used , almost all the new alternators are Chinese so make sure you have a Delco as the other ones the parts in most cases can't be mixed, and the 27 si is not hard to find, contact any rebuilder , I get them for free from my guy , all the parts are out there to construct the version you need, I've built over 12,000 units and never once thought about fixing a rotor, toss it and get another,
 

Tow4

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+1 all new alternators are Chinese. The company i worked for was the largest after market alternator/starter parts supplier and we got out of that because you could get the whole thing for less than the parts it took to rebuild it. Now it's all new units. You can still buy the rebuild parts, but it's usually cheaper to buy a new unit. YMMV.
 

Keith_J

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The autozone DL7157 rebuilt I got is a genuine Delco core. It won't be a waste of time for me to rewind it, nothing special. Just pull the claw pole off the rotor at the drive end, desolder or braze the slip ring connections and the spool should slide off.
I can get the wire for $10 a pound. It should take about two pounds, then it would be an hour of work.
 
Last edited:

glassk

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The autozone DL7157 rebuilt I got is a genuine Delco core. It won't be a waste of time for me to rewind it, nothing special. Just pull the claw pole off the rotor at the drive end, desolder or braze the slip ring connections and the spool should slide off.
I can get the wire for $10 a pound. It should take about two pounds, then it would be an hour of work.
Check over the slip ring wires and where they go to regulator and the turns on rotor are common break points, if it's an open rotor or a knick in insulation can give you a low ohm , since you are into it I know you look at it as a challenge , I have not been inside that one , just know looking for stuff inside of GE 4.1KV motors the brushes and rings on the exciters would be a source of problems, 2cents
 

Keith_J

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I've measured the coil from slip rings to where the magnet wire goes into the coil, open circuit and no short to poles. What had happened to the alternator was a regulator failure and high voltage 14.8+. Full rotor voltage meant uncontrolled current, overheating the rotor. The drive belt was making noise even though it is new and tight.

The nylon bobbin on the rotor looks fine so rewinding it should be easy. While I don't have a specific winding machine, I have a variable speed drill press. And time.
 

Keith_J

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It was the inner coil connection that failed. Unwound the coil to discover. Since the wire is not damaged, it is being reused.
 
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