Review on Tekmar 071 Universal Sensor: Convenient 1' Wire Compatibility by Jose Strong

The original sensor 071 has proven itself as a boiler flow temperature sensor for many years. It eventually failed, which is understandable because it was subject to thermal cycling. At room temperature, the measured resistance is normal, 15.5 kOhm. But as the boiler flow temperature increased, the resistance decreased as expected (as it should work) and fell further below the threshold for the control 422 malfunction error. It is indecent that the DTC 422 for this error on my 422 controller is wrong is. The reported DTC 422 "cooked" with a flashing "!" like an error code. THAT IS NOT RIGHT. 071 failed not because of an open circuit, but because of a short circuit (low resistance) at the terminals of the device.