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Four wires from stator

Discussion in 'The Garage' started by anonymosaurus_RXS, Nov 10, 2020.

  1. Hello all,
    In my pursuit to figure out my charging issue I'm noticing I have four yellow wires coming from my stator, that hooks to a male connector with three yellow wires that continues into the loom. Everything I've read, I'm only seeing that there should be THREE yellow wires coming from the stator and I'm curious as to what this fourth one is doing there and if it could be contributing to my less-than-satisfactory charge?
    So basically I have four wires coming from my stator that run to a female connection, that meets up with a male connection with only three yellow wires.
    My high rev (4-5k rpm) on a full battery only pushes me to 12.7 V, and by bypassing the regulator I can only get up to 13 +/- .4 V at the 4-5k rpm range. when testing for grounding issues on the wires coming from the stator I am getting a reading of 0.8 on my multimeter set to the resistance function at 200. is this a grounding issue from my stator that is contributing to a lack of power sent to the reg/rect? i don't believe i should be getting a reading while grounding to engine from stator wires.
    For context : 1981 Yamaha XS 400 sohc Heritage Special-II, battery is new.
  2. my resistance readings from the three yellow wires that make contact with their male counterparts are reading 0.60 ohms, which is on the lower end of the 0.72 +/- 10%, wondering if this is TOO low and i'm in need of a rewire from my stator. magnet test proves that i am producing a magnetic field on the coils.
  3. 4 wires coming from stator:
    IMG_4386 2.jpg

    connecting to female connection with only 3 connectors that... :

    continues to loom :
  4. The yellow is supposed to go to your turn relay?
    That's the best I can come up with looking at multiple wiring diagrams. In any case, it doesn't seem like it would have any effect on your charging circuit.
    In some schematics I see the yellow wire just capped off, which is essentially what's happening here.
  5. thanks spitfire. seems like a non-issue then.
    any thoughts on my 0.8 ohms reading when testing for grounding from stator wires? connecting red from multimeter to each stator wire while grounding to engine and am reading resistance of 0.8 ohms on 200 ohms setting.
  6. I'm not sure what they are supposed to read, but the fact that all three are consistent would lead me to believe that your stator is not the problem. If one was way out from the other two, or if you got three different readings, I think that would be a different story. Just my two cents.
  7. right on. thinking it’s more related to crappy wiring than anything. i can see a voltage change when revving, just not anywhere close to 13.5 let alone 14 V.
  8. Ok, so I just went to the garage and my stator is on my table and I have OL from any one of the four wire to the point where it would mount/ground to the case.

    Attached Files:

  9. hmmm, i’m getting 0.8 ohms resistance. somethings not right on my end. :banghead:
  10. amc49

    amc49 XS400 Junkie

    Correct, you should be getting infinity at any stator lead with the connector unplugged and checking for grounding.

    Why are you testing at 200 range?, use the lowest you have.

    The extra stator wire is a wye tap and why they did that I have no idea unless pulling off power for something else, it would be a/c not d/c. If the stator leads can be removed from the plastic connector housing then getting the wrong one back in place would mess things up, the wye MUST be the one that ends at the connector and not carried across it. The difference being the resistance from each yellow to each other, the wye one will be about half the resistance of the others.

    If somebody is smart enough you can add another pair of diodes to the wye wire and solder it into the rectifier correctly like the others and have a high output alt that puts out maybe 10-15% more amp. Most cars do that nowadays, using 4 stator leads and 8 diodes now.
  11. looks like i’ve got some more research to do.
    thanks a ton amc49 for the clarification thus far. will update.
  12. 200 ohms reading is the lowest my MM goes.
    connector is unplugged but my stator is still attached to the engine. i don’t think this should offer any differing results though...
    sounds like i’ve got a grounding issue. crappy connections? shitty wires? most likely combination?
    will be digging deep one of these weekends.
  13. amc49

    amc49 XS400 Junkie

    That reading will work, just habit on my part to go as low as I can.
    anonymosaurus_RXS likes this.

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