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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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    I'll have to test that tomorrow after work sorry am home with baby and mrs now. Will update you as soon as possible.
    Oh what should the battery read? That was with the ignition on -> lights on and off.
     
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    Brandon Otte, May 7, 2020
    #141
  2. Brandon Otte

    Brandon Otte Well-Known Member

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    Mmmm I'd have to check that again tomorrow. I'm thinking there could be a bad earth in the lighting wiring somewhere.
     
    Brandon Otte, May 7, 2020
    #142
  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK looking at the schematic, the green/red wire goes to a 4 pin connection which goes to both the temp sensor and there's a thermo switch also in that thermostat housing also - correct
     
    ruckusman, May 7, 2020
    #143
  4. jmw76

    jmw76 Well-Known Member

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    Just the igniton on with no lights on and engine off. Battery will typically read between 12.4 and 13.2V depending on state of charge of your battery.
     
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    jmw76, May 7, 2020
    #144
  5. Brandon Otte

    Brandon Otte Well-Known Member

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    That's a good point, all the more confusing without being able to see everything laid out in front of me. The green and red wire only goes from the sensor to the back of the gauge, I found this out only after I had wired a new wire in. The gauge is grounded from negative to the signal connections on the back of the gauge without any power to it, again only found this out when I had the gauge out. So with ignition on the gauge breaks the circuit so to speak?

    If I may ask - if there was a bad or insufficient earth for the lights, would it find a way to use the gauge earth as an 'extra' path and in doing so cause more current through the gauge and a higher reading?
     
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    Brandon Otte, May 7, 2020
    #145
  6. Brandon Otte

    Brandon Otte Well-Known Member

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    Yup I've connected the sensor wire straight to the battery negative terminal and reads full hot on the gauge. Drops to cold once I disconnect it.
     
    Brandon Otte, May 7, 2020
    #146
  7. Brandon Otte

    Brandon Otte Well-Known Member

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    Yeah totally agree the green with red stripe is the sensor wire, black is earth and brown is positive. Yeah there's already a hard wire fan switch - would that affect it though, I thought it would be completely separate.
     
    Brandon Otte, May 7, 2020
    #147
  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    That's an interesting question, with both the green/red and black wires from the back of the gauge, is there continuity between those two connections on the back of the gauge - to my thinking there shouldn't be as that would affect the gauge reading correctly

    So the straight wire you ran directly to the temp sensor was from the green/red connection on the gauge to the sensor - correct?
     
    ruckusman, May 7, 2020
    #148
  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah the FZR250's are different
     
    my67xr, May 7, 2020
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  10. Brandon Otte

    Brandon Otte Well-Known Member

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    I do know which wires are positive, negative and sensor in case I've been unclear.
    I'll test the voltage at the gauge with lights on and off and report back.
     
    Brandon Otte, May 7, 2020
    #150
  11. Brandon Otte

    Brandon Otte Well-Known Member

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    Yeah there's continuity between the black(negative) and green/red(sensor) at the back of the gauge. That was my thinking but when power is applied there is no longer continuity. Without over thinking it I could imagine that's how the gauge works.
    Yup I removed the green/red(sensor) from the gauge and ran I new wire to the sensor. I since tested the green/red and it only goes from the sensor to the gauge.
     
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    Brandon Otte, May 7, 2020
    #151
  12. Brandon Otte

    Brandon Otte Well-Known Member

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    Would there be any harm in running a test wire from the negative wires at the head light plugs to the battery negative terminal and see if that eliminates the gauge jump?
     
    Brandon Otte, May 7, 2020
    #152
  13. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK, I was suggesting doing that test of purely the gauge internals, so with the wires disconnected
     
    ruckusman, May 7, 2020
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  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Sorry for being lazy and not reading all of the previous 8 pages. I recall you said the the PO had done some dodgy wiring mods to the tailight/brakelight. Could you humour me & just disconnect all of that then repeat your test again please. I always blame the owner first when anything goes wrong with a bike (ask @Linkin he should be getting used to it by now).
    Cheers
    Blair
     
    maelstrom, May 7, 2020
    #154
  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    long story short - the gauge is reading too high and jumps up when lights are turned on, thought we had it sorted, however the problem returned when Brandon plugged the headlights back it

    The issue is a secondary current path from the gauge sensor wire to ground, it isn't a direct short to ground, but allows extra current flow, which increases further with the headlights on

    Apparently the thermo switch has been bypassed with a hard wire switch on the dash or thereabouts to switch the cooling fan on
     
    ruckusman, May 7, 2020
    #155
  16. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Remove the dodgy bro's fan switch and make everything standard.
     
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    Linkin, May 7, 2020
    #156
  17. Brandon Otte

    Brandon Otte Well-Known Member

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    Yeah I’ll try unplugging the extra tail indicators and fan switch tomorrow. Tonight I’m going to try running an extra ground from the headlights to battery negative just so I know. The fan switch is wired from the original sender unit - the PO has unplugged the sender and put a switch in its place so don’t think that’ll do it but I totally agree with returning everything to standard.
     
    Brandon Otte, May 8, 2020
    #157
  18. Brandon Otte

    Brandon Otte Well-Known Member

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    So with that extra ground from one of the two headlight plugs direct to the battery negative the gauge no longer jumps when lights are turned on.
    Would it be safe to assume either there’s a poor earth somewhere in the loom from corrosion or the PO wiring?
    And would it be safe to run a new permanent earth wire from that headlight loom to battery?
     
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    Brandon Otte, May 8, 2020
    #158
  19. Brandon Otte

    Brandon Otte Well-Known Member

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    There is the slightest rise on the gauge when lights are turned on but I’m guessing with a decent earth wire that’ll help?
     
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    Brandon Otte, May 8, 2020
    #159
  20. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I would go direct to the frame.. not the battery.
     
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    Andych, May 8, 2020
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