ASE A7 Heating Air Conditioning Practice Test

Diagram of automotive ac control circuit.

6. Component A in the electrical diagram above has all of the following characteristics EXCEPT:

  • A. It is a Negative Temperature Coefficient sensor.
  • B. It is a thermistor.
  • C. It is a variable resistor.
  • D. It is a switch.

6.

ECT sensor

Answer A is wrong. An ECT sensor is an (NTC) Negative Temperature Coefficient sensor.

Answer B is wrong. An engine coolant temperature sensor is a thermistor.

Answer C is wrong. An engine coolant temperature sensor is a variable resistor that modifies a 5 volt reference signal from the control module. Resistors are used to limit or control current flow (as well as voltage) in circuits.

Answer D is correct. It's a sensor, A/C systems use switches that are either open or closed. They don't modify reference signals like sensor's do.