Thermo unit and thermo sensor replacement

Discussion in 'Electrical' started by Mightymouse, May 14, 2019.

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  1. May 14, 2019 #1

    Mightymouse

    Mightymouse

    Mightymouse

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    Hey,

    I have a 1997 VMX1200JC. This will be the second year I have owned it. It's got about 63,000 miles on it.

    I noticed two odd things since I've owned this bike regarding the coolant system.

    1. Upon startup, the temperature gauge needle does not move as the engine warms up. When the engine is warm, I can "fix" the temperature gauge by tapping it. That'll get the needle to move.
    2. On a hot day in traffic, sometimes the engine stalls if I'm not moving.

    These symptoms made me wonder if the thermo unit (part #11H-83591-00-00) and thermo switch (part #3LN-83560-01-00) were bad.

    I removed both from the coolant manifold and tested each per the procedure in the Claymer manual (pages 344-345) (ISBN-13: 978-1-59969-650-8).

    I discovered the thermo unit was bad. The resistance was greater than the specifications listed in Table 2. I ordered a new one.

    I was unable to determine if the thermo switch was bad. I could not get the coolant hot enough to test the continuity of the switch (221 degrees F).

    So, I reasoned if the thermo unit was bad, there may be a chance the thermo switch is bad as well.

    So, I ordered a new one.

    Partzilla.com charged $104 for both. Shipping and taxes included.


    Now I'm waiting for the parts to come.


    Has anyone else gone through this? Do these thermal sensors go bad with age?
     
  2. May 14, 2019 #2

    Mightymouse

    Mightymouse

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    And uh....how do you use a micrometer to test the water temp gauge?
     

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  3. May 15, 2019 #3

    maleko89

    maleko89

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    The thermoswitch is for the radiator fan. As long as the fan pops on before it gets to the red line on the temp gauge, it's fine. The thermo unit (smaller of the two) is for your temp gauge. I've never seen one go bad. Usually it's either the gauge itself or the ground wire which attaches to the top of the coolant manifold near the coolant cap.

    Mark
     
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  4. May 15, 2019 #4

    sdt354

    sdt354

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    A multi-meter with a thermal adapter me thinks.
     
  5. May 15, 2019 #5

    Mightymouse

    Mightymouse

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    Thanks. I'll take a look at the ground wire. There might be some corrosion where it connects to the coolant manifold.

    I thought the gauge might be suspect as well. I lightly sanded the electrical terminals that connect the thermo unit to the water temp gauge. The continuity of each wire was good.

    I'll let ya know how it goes.
     
  6. May 15, 2019 #6

    Mightymouse

    Mightymouse

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    That'd be a sweet tool to have.
     
  7. May 16, 2019 #7

    mabdcmb@yahoo.com

    mabdcmb@yahoo.com

    mabdcmb@yahoo.com

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    It looks like you could connect a 12VDC source to the gauge where the BR wire attached.
    You would then need to run a wire from the GR terminal to a variable resistor (potentiometer) that you can tune between 20 OHM and 160 OHM and land it on a ground.

    Apply power and adjust the resistor to check gauge function. There is nothing in the manual that correlates a certain temp with a certain gauge reading but, if you have low resistance in the circuit (26.2-29.3 Ohm) the gauge should be up by the red zone as this would be a temp of 212F. If you raise the resistance to 153.9 ohms the gauge should be way down at the bottom as this would be a temp of 122F.
     

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  8. May 17, 2019 #8

    sdt354

    sdt354

    sdt354

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    Or an infredheat gun will do the trick. Harbor Freight has them cheap.
     

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