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Question about Reg/Rect wiring

Discussion in 'XJ Technical Chat' started by baz666, Apr 3, 2010.

  1. baz666

    baz666 Member

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    Hello all,
    I have a spare XJ750 regulator/rectifier that I want ot adapt to an '83 Suzuki GS750ESD I bought a week or so ago. The GS series had notoriously weak Reg/Rect units and a common nod is to replace them with much sturdier units from Hondas or Yamahas. The Suzuki unit is simple, it has the 3 yellow wires to the stator, a red power wire and a black ground wire.
    The Yamaha unit is very similar. 3 white wires to the stator, a red power wire, a black ground wire - but then it's got a brown wire and green wire as well. Anybody know what purpose the green and brown wires serve?
    I checked the wiring diagram and they both seem to go to a plug then off into the harness and as far as I can tell, to the front turn signals. Some Reg/Rect units have a 'sense' wire that monitors 12V power in the electrical system but I'm not sure that's the purpose the green or brown wire serve.
    Any help at all would be appreciated.
    thanks,
    baz
     
  2. markie

    markie Member

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    The brown and green wires on a Yamaha regulator control the strength of the "Field" winding, which is on the rotor, and connected via the alternator brushes.

    If the Suzuki unit doesnt have these wires, it CANNOT be used.Check the service manual for this.

    You can use a later regulator/rectifier from a SECAII model as this uses Thyristor control and a PERMANENT MAGNET alternator.

    Trust me - this is what is fitted to my XJ600! A PO had fitted and earlier regulator and the result was the battery was being "Cooked" as it was charging flat out all the time.

    I do have a picture of the 4 and 5 terminal SECAII connections if you buy one.
     
  3. baz666

    baz666 Member

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    Well, I don't know what's going on but I spliced in the XJ750 Reg/Rect to my 83 GS750ESD and the bike started up fine, measures 13.5 at idle. I rode it around this afternoon and stopped several times for errands, etc.
    The bike restarted every time without a problem. It seems the battery is being charged, which was the original problem with the faulty Suzuki Reg/Rect. The extra two wires coming out of the XJ alternator, the green and brown. The Brown I hooked up to the suzuki's brake light wire and the green I ran as a ground to the chassis. Seems to work so far. I'll keep my fingers crossed.
     
  4. markie

    markie Member

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    Baz, I just edited my post - It will "Work" but there will be no regulation - it will charge at maximum all the time.

    I found the electrolyte level dropped rapidly on my battery.

    This diagram shows where they are supposed to go

    [​IMG]
     
  5. MiCarl

    MiCarl Active Member

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    To expand on what Markie said:

    Your Suzuki has a permanent magnet alternator. The alternator output is determined by engine speed. More RPM = more output. The Voltage regulator on that type drains excess power to ground to keep the voltage in the system from going too high.

    Your XJ has a field coil alternator. The output of the alternator can be increased or reduced by controlling the voltage to the field coil. The XJ regulator uses the extra two wires to control that field so the alternator only produces as much power as the system needs.

    Both types have the rectifier that converts AD to DC built in.

    You are only using the rectifier from the XJ regulator/rectifier. The voltage is uncontrolled. You are likely to ruin the battery and shorten the life of other electrical components.
     
  6. markie

    markie Member

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    Glad we are talking the same type of language! I found that on my bike a previous owner had cut short the brown wire and ripped out the green. B4st4rd!

    I paid £15 for the right regulator and it's working fine.
     
  7. baz666

    baz666 Member

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    Well, that makes sense. Since the Suzuki R/R units are known to be weak, I'll look for a Seca II R/R or I've read the 5-wire models from later Kawi ZX bikes will work as well.
    thanks for your help.
    baz
     

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