T120 Charging Problems

Discussion in 'Bonneville' started by Swampdweller, Feb 7, 2024.

  1. Swampdweller

    Swampdweller New Member

    Aug 13, 2017
    17
    3
    Cambs, England
    #1 Swampdweller, Feb 7, 2024
    Hi,

    I have a t120 2016 with various charging problems,
    the first thing I noticed was that the trip had stopped working then the abs and engine management lights came on then the bike cut out and refused to start,
    two of the three wires going to the back of the block connector on the reg/rec from the stator have broken,
    I have since fitted a new block connector,
    the reg/rec is charging at 14.3 volts at the battery but it doesn't vary from tick over to four thousand revs
    the resistance at the back of the new block connector [three wires] going into the reg/rec is 1.4 ohms
    on all three wires, my Haynes manual states 0.14 to 0.18 ohms, i checked the battery on a drop tester
    which showed the battery was failing, so I now have a new battery.
    Do you have any ideas, I tried a working reg/rec but with the same results. 14 volts but not increasing with the revs.

    Ian
     
    • Agree Agree x 1
  2. nickjaxe

    nickjaxe Active Member

    Sep 2, 2020
    72
    28
    Cheshire UK
    #2 nickjaxe, Feb 12, 2024
    14.3v sounds good to me...no matter what RPM.
     
    • Agree Agree x 2
  3. RevPaul

    RevPaul Senior Member

    Apr 21, 2020
    863
    243
    Cheshire, UK
    #3 RevPaul, Feb 12, 2024
    Isn’t that the point of the rectifier/regulator? The rectifier rectifies the ac output of the alternator to DC, the regulator regulates the now DC voltage to a constant 14v or so, to keep the battery charged and the electric consumers fed.
     
    • Agree Agree x 1
  4. nickjaxe

    nickjaxe Active Member

    Sep 2, 2020
    72
    28
    Cheshire UK
    #4 nickjaxe, Feb 12, 2024
    Exactly......and it seems its doing just that.
     
    • Agree Agree x 2
  5. Iain Griffin

    Iain Griffin New Member

    Jan 15, 2024
    5
    3
    WHITTLESEA
    #5 Iain Griffin, Mar 6, 2024
    Hi,

    most reg/rec start at over 13v and increase with the revs up to 14.50-14.75
    the higher resistance from the stator to the reg/rec came down to corrosion at the battery earth lead engine end, the two broken wires going into the block connector from the stator going into the reg/rec have been fixed with a new block connector, I see the new t120 models have the reg/rec on the frame not on the headstock, so all is well now,
     
    • Like Like x 1
    • Agree Agree x 1
  6. nickjaxe

    nickjaxe Active Member

    Sep 2, 2020
    72
    28
    Cheshire UK
    #6 nickjaxe, Mar 11, 2024
    It also controls the amps going into the batt.....the volts may stay over 13v but the amps need to drop to next to nothing as the battery is charged.
     
    • Agree Agree x 1
    • Love You Love You x 1
  7. Iain Griffin

    Iain Griffin New Member

    Jan 15, 2024
    5
    3
    WHITTLESEA
    #7 Iain Griffin, Mar 11, 2024
    The amps are fine, the voltage was the problem now fixed.
     
    • Like Like x 2
  8. Brixton Steve

    Brixton Steve Member

    Sep 21, 2019
    46
    18
    Devon
    #8 Brixton Steve, Apr 24, 2024
    Hi Swampdweller.
    Got same problem .How did you go about fixing this? Did you extend the too short wires or just fit existing wires into a new connector. Can you give a step by step of what you did pls.
    Would be interested to know what mileage you've done. Mine is a 2019 model with 21k on the clock.
    Thanks .
    Steve.
     
    • Like Like x 1
  9. Iain Griffin

    Iain Griffin New Member

    Jan 15, 2024
    5
    3
    WHITTLESEA
    #9 Iain Griffin, Apr 26, 2024
    Last edited by a moderator: Apr 27, 2024
    Hi Steve, to solve the problem webbs Peterborough found me a short loom
    from a 675 three cylinder bike from the reg/rec to the loom having both three and two wire block connectors and the wires to the block connectors on the main loom, I simply removed the three wire section including the two block connectors and replaced the part on my bike from the reg/rec into the main loom under the tank, adding about two inches to the length to stop the wires from stretching/shearing, then after soldering re wrapped the loom, hope this makes sense if you want i can try and find the part number, the bike has 12k on the clock, if you need anymore help let me know.

    regards..
     
    • Like Like x 1
  10. Brixton Steve

    Brixton Steve Member

    Sep 21, 2019
    46
    18
    Devon
    #10 Brixton Steve, Apr 30, 2024
    Many thanks for the info, thats a great help
     
Loading...
Similar Threads - T120 Charging Problems
  1. Servodyne

    T120 2016 Charging/starting Fault

    Servodyne, Jan 17, 2021, in forum: Technical Help
    Replies:
    10
    Views:
    1,515
    Tricky-Dicky
    Jan 18, 2021
  2. rich

    Charging issues on a 72 Bonnie T120

    rich, Sep 17, 2014, in forum: Bonneville
    Replies:
    0
    Views:
    966
    rich
    Sep 17, 2014
  3. lolachampcar

    St1200rs Seat

    lolachampcar, Sep 13, 2025 at 11:14 PM, in forum: Speed Triple
    Replies:
    0
    Views:
    117
    lolachampcar
    Sep 13, 2025 at 11:14 PM
  4. Ahçaira

    2022 T120, No Hi Beam

    Ahçaira, Aug 30, 2025, in forum: Technical Help
    Replies:
    4
    Views:
    235
    Ahçaira
    Sep 7, 2025
  5. RBinDevon

    Picking Up A New T120 1 Sept.

    RBinDevon, Aug 24, 2025, in forum: Bonneville
    Replies:
    4
    Views:
    416
    Rob B
    Sep 11, 2025 at 10:41 PM

Share This Page

Sign up