Test purpose:This test is designed to monitor the voltage of the thermistor and determine if it iswithin range of the operating specifications. Thermistors are either NTC or PTC typeand their resistance values are variable depending on the temperature that they aresensing. A thermistor can either be open, shorted or operating correctly orincorrectly. In this test we are looking to determine if the resistance change in thethermistor is smooth and consistent over the increase and decrease in temperature.Although this test is not a definitive “pass / fail” or “green light / red light” the tool isautomatically set up for a fast voltage capture with stable readings and rangedcorrectly. Once connected to a thermistor, the graphing screen will be the way tomonitor output.Tool Setup:• Top Chanel: N/A• Bottom Channel: Voltage DC ranged at 60V• Set Min/Max to Max• Speed: 64MS (256) or (4000 Hz 256 SMPL)Test Procedures:• Place Leads on tool to Voltage DC• Use Probe Tips on leads or clamps• Connect the positive probe tip or clamp to the positive output of thethermistor• Connector the ground probe tip or clamp to the ground of thethermistor• Look for “out of range” , “0” Volts or a voltage reading.• Set the Meter Mode to Graph• Begin to heat up the thermistor.• Watch the characteristics of the reading for a gradual change in thevoltage.Automotive ApplicationsThermistor VoltageCuriosityRecommendationsA thermistor is not actively powering itself, but rather creating a voltage dropacross itself based on temperature. A faulty thermistor reading on the vehicle maybe the cause of the thermistor, the thermistor circuit, or the computer monitoringthe thermistor value.Diagnosis of a thermistor should be broken into the 3 categories of component,circuit and computer.Diagnosing the thermistor:• A thermistor can either be open, shorted, operating correctly or incorrectly.• If the thermistor is open, the reading will be “out of range” or a the tool will seeghost voltage (a fluctuation of voltage randomly from the air and otherelectronics around us).• If the thermistor is shorted it will either see 0 volts on the screen or at least avoltage reading that does not change due to the nature of how voltmeters work.• If the thermistor is operating incorrectly, the changes in its internal resistancevalues will change sharply as consistent temperature is applied to the elementand the readings will appear to “jump” or “drop”significantly as element is beingheated and monitored.Diagnosing the circuit:If the thermistor is found to be operational or operating as expected but the issuestill exists the next step is to diagnose the thermistor circuit.• Begin with the connectors, then the feeds or cables and end with the grounds.• Visually inspect and wiggle test the circuits.• Use the “loaded cable” or “cable tests” from the voltage drop menu to verifythere is no undue voltage drop on the system. (If possible and safe a loadedtest of the cables disconnected from any computer circuits would bepreferable.)• If the problem still exists, attempt to diagnose the monitoring system of thethermistor using a wiring diagram to identify what is monitoring the thermistorvalue.