WaterFurnace low water flow

Discussion in 'Maintenance and Troubleshooting' started by DugMan, May 25, 2014.

  1. DugMan

    DugMan New Member

    Hi -

    I have a WaterFurnace ATV034, placed into service in 1993. that has been almost nearly free. I am getting a low water flow fault on the LED panel. I have about 30 PSI in the horizontal loop, and I know that the water is circulating. I have read on several forums that a thermistor could be defective, giving a false freeze reading to the controller. I have not yet removed the thermistor to test, (it is not easy to get to), but the leads are identified and accessible. I would like to eliminate all that I can before I call for service.

    Is the thermistor a common failure point? What is the best way to check this? Can it be taken out of circuit (replaced with a fixed resistor) to confirm failure of the thermistor?

    If not the thermistor, what else should I look for?

    Thanks in advance.
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome.
    You need to verify the flow before the next step on the diagnostic tree. Measuring the pressure drop acrossed the coil and comparing to the chart in the book while the unit is running will verify if you have flow or not.
  3. Home Owner SIMPSON

    Home Owner SIMPSON New Member


    I have exactly the same unit and the same problem! Here is how I solved the problem:

    On the side of my service panel I Posted the following notice:

    Water flow light will come on
    In early spring when the frost leaves the ground!
    Reset the unit ... This might go on for 2-3 weeks!

    The BOTTOM LINE IS THIS: The unit is just doing what it was design to do... Shuting down if the fluid in the loop is too cold! This will happen if your unit sits very long before going into the next cycle. Resulting in the loop picking up the frozen ground temp!

    To make my unit run more I just run my HRV SYSTEM MORE IN THE SPRING TIME CAUSING THE Geo unit to run more but it doesn't shut down!

    great unit!

  4. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Hello and welcome.

    The last WF low water flow fault I worked on was caused by low refrigerant.

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