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Help FZR250 Temp gauge rises when lights are turned on?

Discussion in 'Yamaha 250cc In-Line 4's' started by Brandon Otte, Mar 12, 2020.

  1. Brandon Otte

    Brandon Otte Member

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    Hi again everyone,

    So the issue I'm having is when I turn my lights on the temp gauge jumps up about a quarter of the gauge depending on how warm it is.

    Seems the warmer it is the more the gauge moves.

    With the lights off the gauge will work its way up to around the half way mark which appears normal but with the lights on it reads 3/4 to just under the red zone.

    The previous owner hard wired the radiator fan to a switch on the dash, not sure if that's because the thermo switch failed or what but I have just installed a replacement thermostat assembly to try eliminate the thermostat.

    Could it be possible that a ground on the dash cluster is no good?

    Any help will be greatly appreciated!

    P.s also looking to source the exup valve cables.

    Thanks
     
  2. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    First thing I would check would be the bullet connector on the thermostat housing to make sure the connection is good.
     
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  3. Brandon Otte

    Brandon Otte Member

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    Is that the connector to the temp sensor?
    If so I have checked it, played around with it and it was either connected or not.
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    My FZR250R temperature would read slightly low when the engine was running
    I found that the thermostat earth lead terminal on the end of the wire had corrosion inside, cleaned it up and it started reading normal again.
    Mine run's on 1/4 or just above the first line

    This same earth is also used for the tail light's

    Use some dielectric grease in between the bolt/terminal and frame to stop it from happening again

    [​IMG]

    Cleaned up and some dielectric grease applied

    [​IMG]
     
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    Last edited: Mar 24, 2020
  5. Brandon Otte

    Brandon Otte Member

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    Hi my67xr,

    Thanks for that I have hope now!

    Where is the earth wire found exactly though, you say the thermostat earthing wire, but, I can't seem to find it.

    Where about on the frame is it bolted and where on the thermostat housing?

    Cheers,



    Brandon
     
  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    It's pictured above your post,
    the thermostat housing is earthed to the frame via the main harness, through the black wire coming off the thermostat housing top cover, there is a pair of terminal's joining the wire about 80mm away from the mounting bolt, the black wire then run's into the main harness and is earthed near the back of the engine to the frame
     
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  7. Brandon Otte

    Brandon Otte Member

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    I had my thermostat housing off the other day to replace the thermostat, it didn't have any earth wire attached to it. I'll have a look around the engine bay, maybe that's the issue.

    Thanks will let you know once I've had a look at it.
     
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  8. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Often they are just on a eyelet terminal and the other end is a bullet connector to the harness. Easy to lose.
     
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  9. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Thats all it is

    thermos.jpeg
     
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  10. Brandon Otte

    Brandon Otte Member

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    Very helpful thank you!
    Yeah mine is definitely missing it, I'll see what I can do over the next few days :)
     
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  11. Brandon Otte

    Brandon Otte Member

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    Hi guys just a thought @my67xr @GreyImport I didn't mention my fzr250 is the 2kr model.
    I'm assuming they also had the earth wire on the thermostat housing?

    I'll be at my 'other' home tomorrow waiting delivery of my leather jacket so can check my bike then.

    Again cheers for all your help this forum is so good!
     
  12. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    2kr Part's Catalogue doesn't show a seperate wire for the thermostat housing earth like the 3LN's run,
    but there still may be a black wire coming directly off the harness with a ring terminal, the temp sender unit still need's to run through an earth unless there's a mounting bracket from the thermostat housing to frame
     
  13. Brandon Otte

    Brandon Otte Member

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    Ahh okay, there's no mounting bracket so surely there's something. I also read on another post mentioning flickering temp gauge readings and how the temp gauge may have earthing problems to the frame.
    Can't wait to check it out tomorrow!

    I've also read that Nulon pre-mix coolant is the way to go so will definitely be grabbing some asap. As for oil I'm still reading up on the options, is it true Delo 400 is the way to go?
     
  14. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah there's a few user's here running the Delo 400 15W40 (Not Delo Silver / Gold).


    I run Penrite MC 4ST 10W30 in my 3LN3, it rarely get's below 0 or above 50 degree's, highly doubt i'd be out riding in either of those temp's if it did too.
    $44.30 at Supercheapauto normal price for 4L but i got mine on for $31 when it was on special @ 30% off
    https://www.supercheapauto.com.au/p...oRs5FJBVjiIgBbS9JLYaApbHEALw_wcB&gclsrc=aw.ds


    This is from the 3LN Service Manual

    [​IMG]
     
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