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.