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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.

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  1. Brandon Otte

    Brandon Otte Well-Known Member

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    Thanks for the suggestion am about to start pulling bulbs. It’s a single wire and with it disconnected it drops to zero.
    Quick note I noticed when I turn the ignition on the gauge goes from the very lowest position(below zero?) to the minimum mark. Is that normal?
     
    Brandon Otte, May 6, 2020
    #81
  2. Brandon Otte

    Brandon Otte Well-Known Member

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    Yeah I tried that last night with no luck. Was exactly the same. I connected a wire from the thermostat housing bracket bolt to the negative terminal. Shall I try hold it on the sender body itself?
     
    Brandon Otte, May 6, 2020
    #82
  3. Brandon Otte

    Brandon Otte Well-Known Member

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    Ahh I see what you’re saying! I’ll try that and get back to guys thank you!
     
    Brandon Otte, May 6, 2020
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  4. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK, don't connect the ground connection on the gauge directly to earth, normally the temperature sensor is in that circuit to limit the current with it's resistance, you may damage the gauge or blow a fuse, or both

    What I was intending to suggest, perhaps not that clearly, is check the wire that goes from the negative on the gauge, removed of course, and have it disconnected from the temperature sensor also to see if there is any connection whatsoever to ground on that wire - there shouldn't be with it disconnected at both ends
     
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    ruckusman, May 6, 2020
    #84
  5. jmw76

    jmw76 Well-Known Member

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    I had a look at a wiring diagram and I believe the gauge has 3 terminals. 1 connects to ground, 1 connects to the temp sender output and the other connects to +ve (maybe via an instrument voltage regulator. did not check that thoroughly). Is this correct?
     
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    jmw76, May 6, 2020
    #85
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Correct, it does have 3 terminals - check

    https://www.2fiftycc.com/index.php?...lights-are-turned-on.10840/page-4#post-132771

    Not sure what the third terminal is for, it would be good to have resistance readings between terminals, resistance readings from the terminal wires to ground and voltage readings at those wires with the power switched on

    The green and brown (is it orange) one is a mystery
     
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    ruckusman, May 6, 2020
    #86
  7. Brandon Otte

    Brandon Otte Well-Known Member

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    Oh I meant I tried a wire from the thermostat housing to the battery negative, I had to be home early tonight to look after baby otherwise I was going to try a negative straight from the gauge to the battery... phew
     
    Brandon Otte, May 6, 2020
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  8. Brandon Otte

    Brandon Otte Well-Known Member

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    Instrument voltage regulator? I tested the voltage to the instrument cluster the other night and found it had the full 14volts which dropped to 10volts with the lights on. I did wonder if I could just direct wire the gauge to the battery positive and negative but maybe that's not wise?
     
    Brandon Otte, May 6, 2020
    #88
  9. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Yeah I would check what resistance you have to ground through the thermostat itself before wiring directly to the battery negative

    Going from the gauge ground connection straight to ground might not cause damage to the electrics or the gauge, but I expect that the gauge would shoot straight up to peak temperature if our prior assumptions are correct

    EDIT - just re-read your post, D'OH, apologies, yes you could try straight to battery ground from the temperature sensor housing

    Sorry I misread that as from gauge ground straight to battery ground which would bypass the temperature sensor
     
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    ruckusman, May 6, 2020
    #89
  10. Brandon Otte

    Brandon Otte Well-Known Member

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    Green and brown - signal from the temp sender? (green and red)
    IMG_4679.JPG
     
    Brandon Otte, May 6, 2020
    #90
  11. Brandon Otte

    Brandon Otte Well-Known Member

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    So here are a few photos;
    Tail showing the indicators up top and the extra indicators the PO installed. IMG_4690.JPG
    That wiring has been messed with at some point, not sure why there is a block connector there and where that plug with brown and red wires go to. Haven't tested it yet though. IMG_4692.JPG
    And looking under the passenger seat - those wires go to the left and right indicators, respectfully. IMG_4693.JPG Just trying to give as much information as possible.

    I was hoping I could give the gauge a positive and negative wire direct from the battery but will that damage it?
     
    Brandon Otte, May 6, 2020
    #91
  12. Brandon Otte

    Brandon Otte Well-Known Member

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    I haven't pulled light bulbs yet, hopefully tomorrow or the weekend. I need to know if I can run power and/or only earth direct to the temp gauge without an instrument regulator, and does the temp sensor need to be apart of the same circuit?

    My aftermarket gauge wiring diagram shows straight 12v positive, negative(ground) and sensor running on the same ground as the power.
     
    Brandon Otte, May 6, 2020
    #92
  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    So the purpose and destination of our mystery wire, may be the brown, or may be the green with red stripe - which is the mystery wire

    I tried reading the B&W schematic, no point unfortunately as I cannot decipher Japanese and I checked the translated Zeal schematic, it doesn't have the temperature gauge
     
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    ruckusman, May 6, 2020
    #93
  14. Brandon Otte

    Brandon Otte Well-Known Member

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    @ruckusman okay I'm following now, so I mustn't wire negative from the gauge direct to battery?
     
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    Brandon Otte, May 6, 2020
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  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK - so the ground goes through the temperature sensor for the other gauge also, it's that ground which seems to be compromised somehow allowing through too much current AND allowing through even more current with the lights on
     
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    ruckusman, May 6, 2020
    #95
  16. Brandon Otte

    Brandon Otte Well-Known Member

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    Would I be able to wire the gauge and sensor on their own loom to the battery?
     
    Brandon Otte, May 6, 2020
    #96
  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Gauge ground through the temperature sensor
     
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    ruckusman, May 6, 2020
    #97
  18. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    The gauge may be stepped down voltage, might not be 12v ?
     
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    my67xr, May 6, 2020
    #98
  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Wondering that - the voltage and origins and destination of all three of those wires needs to be sorted, although 14v - dropping to 10v with the lights on has been measured at the gauge
     
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    ruckusman, May 6, 2020
    #99
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's a lot of voltage drop. I'd be looking for a poor connection or wire with broken strands somewhere.
     
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    Linkin, May 6, 2020
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