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Thread: Is my thermistor bad? OHM reading question

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    Is my thermistor bad? OHM reading question

    I have an Aqua Rite SWG model X296. When I turn the pump on the no flow light flashes as it normally does and the salt reading shows. After about a minute the no flow light goes off and the generating light comes on for about 10 seconds and then goes off. The power light never comes on. After doing some reading I'm hoping that it's just the thermistor. I looked at it and don't see any cracks, etc. I haven't taken the board out yet to see if there are any burn marks on the back. I did check the resistance with the power off to the board and got a reading of about 2.5 ohms (if I'm reading my multimeter correctly). Would that indicate a problem? Just trying to see if I should order a replacement and solder it myself, which I'm comfortable doing, or if that's a good reading and not my problem. Thanks in advance for any input.

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    Re: Is my thermistor bad? OHM reading question

    What are the diagnostic readings?
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    mas985's Avatar
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    Re: Is my thermistor bad? OHM reading question

    Welcome to the forum!

    The normal operation range for a 10k thermistor is 33k@32F to 5.8k@100F. But how did you measure the thermistor in the cell? Through the connector?

    Right before my last cell failed, the thermistor failed first and I bypassed it for a few months with a 10k resistor. Worked fine except the salt readout wasn't correct.
    Mark
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    Re: Is my thermistor bad? OHM reading question

    He means the inrush current limiter on the circuit board.

    AS322R025 or SL322R025

    Also, you could have installed a 10k thermistor in the pipe right before the cell and spliced that into the the thermistor wires.
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    mas985's Avatar
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    Re: Is my thermistor bad? OHM reading question

    I didn't want nor need to put an extra hole in the pipe.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Is my thermistor bad? OHM reading question

    OK, just suggesting it as an option. It would provide the correct temperature, which would allow the system to calculate the correct salinity.
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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    What are the diagnostic readings?
    The readings with the pump running were: 72, 0.0, 0.00, 43P, -0, AL-0, r1.40. Let me know if there is something else that you need to help me. Thanks.

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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    He means the inrush current limiter on the circuit board.

    AS322R025 or SL322R025

    Also, you could have installed a 10k thermistor in the pipe right before the cell and spliced that into the the thermistor wires.
    Correct, it is the inrush current limiter. I believe mine is the SL322R025.

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    Re: Is my thermistor bad? OHM reading question

    Zero volts points to a bad thermistor. Look for a hairline crack.

    A failed thermistor won't always be obvious.

    I think that the thermistor is bad. However, here is a diagnostic manual if you want to do some tests.

    https://www.hayward-pool.com/pdf/man...iagnostics.pdf
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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    Zero volts points to a bad thermistor. Look for a hairline crack.

    A failed thermistor won't always be obvious.
    Thank you, James. I didn't see a crack but of course that doesn't mean it's not there. Does the ohm reading I got mean anything or help point to a bad thermistor? And just to be clear, the SL322R025 is the thermistor you are talking about, correct? Thank you again.

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    Re: Is my thermistor bad? OHM reading question

    SL322R025 is correct.

    Try this:
    Move the switch to off and check volts. Then move the switch to auto and see what the voltage does.

    Also, I posted a link to a diagnostic manual above.
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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    SL322R025 is correct.

    Try this:
    Move the switch to off and check volts. Then move the switch to auto and see what the voltage does.

    Also, I posted a link to a diagnostic manual above.
    Moved switch to off and volts were 0.0. Moved switch to auto and voltage stayed 0.0

    Then I turned power off and jumped the legs of the thermistor and powered on with the switch in the off position. Green power light light up, which it wasn't doing before, and voltage went to 30.6. So sounds like that confirms the bad thermistor. Have powered off and will order one and replace it.

    Thank you so much for your quick replies and very helpful diagnostics. Much appreciated.

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    Re: Is my thermistor bad? OHM reading question

    Yes, bad thermistor.
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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    Yes, bad thermistor.
    I got a new thermistor and installed it and everything seems to be working again, thank you!!

    I do have a question though. When I was removing the board I took pictures before disconnecting but of course the one wire that wasn't totally clear in my picture is the one I'm not sure about. I've attached a picture of it as I don't know what it is or what it does. As I was removing the plug from the PCB the wires came out of the jumper and I'm not 100% I put them back in correctly. It is the two twisted black wires that go to J8 on the PCB and attach to the small black square you see with the gold cylindrical thing next to it. Thanks again.

    20170326_124348.jpg20170326_124355.jpg

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    Re: Is my thermistor bad? OHM reading question

    AQR-X296 is a model of Aqua Rite for arid climates. It supports higher temperatures and salt levels. It includes a fan.

    I haven't seen the wires before. They must be specific to the AQR-X296.

    The black square is a rectifier. I'm not sure what the gold thing is. Maybe a high limit for temperature?
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    Re: Is my thermistor bad? OHM reading question

    Quote Originally Posted by JamesW View Post
    AQR-X296 is a model of Aqua Rite for arid climates. It supports higher temperatures and salt levels. It includes a fan.

    I haven't seen the wires before. They must be specific to the AQR-X296.

    The black square is a rectifier. I'm not sure what the gold thing is. Maybe a high limit for temperature?
    I'm in Arizona so that would make sense. I'll check with some of the pool stores around here to see if they know. Thanks again.

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