Test the thermistor by turning the Engine ON and the Air Conditioner ON.

Using a Voltmeter (set to DC Volts), the Green/Orange wire will have battery voltage (around 13.5vdc) from fuse #29 in the under hood fuse box.

The Blue wire will have battery ground from the AC control assembly.

The most important wire is the Blue/Black wire. The Voltmeter will show less than .5 volts with the thermistor on (temperature above 45 degrees F). It will show a nominal 4-5 volts with the thermistor off (temperature below 40 degrees F).

During inital operation, the temperature at the evaporator will be above 45 degrees and the Voltmeter should read less than .5 volts. When the temperature of the evaporator is below 40 degrees F, the Voltmeter will read 4-5 volts which turns the Air Conditioner Compressor OFF. This keeps the Evaporator from freezing.

If your Thermistor is reading 4-5 volts when you first turn the AC on then your Thermistor is defective and needs to be replaced.