HVAC Advanced Diagnosis (LV3)

A. General Topics:

Air is flowing from the defrost vents only. What can the technician do to isolate the concern?

• Test the mode doors.

• Test the evaporator sensor.

• Check for restricted cabin air filter.

• Replace the distribution box.

A. General Topics

A vehicle is brought in for clicking and popping noises heard during HVAC mode selection from the instrument area. After the concern is verified, what is the most likely cause of the findings?

• Actuator gears stripped

• Mode door loose

• Recirculation door binding

• Blower motor binding

A. General Topics

What would a technician use to diagnose the humidity sensor?

• An infrared digital thermometer

• An A/C recovery and recharging station

• A scan tool and a steaming cup of hot water

• An analog amperage meters

A. General Topics

How would a technician diagnosis the in-car temperature sensor?

• Test the sensor with a scan tool and ultraviolet light

• Measure the refrigerant pressure with an A/C recovery and recharging station

• Test the resistance of the sensor with a digital multimeter

• Perform a current draw test on the HVAC module

A. General Topics

What would the technician use to diagnose the sun load sensor?

• A steaming cup of hot water

• A temperature probes

• A fluorescent lamp

• An ultraviolet light

A. General Topics

What is the best way to diagnose the outlet temperature sensor?

• Measure the current draw of the outlet temperature sensor.

• Use an A/C recovery and recharging station to check A/C pressure.

• Display the temperature sensor parameters on the scan tool.

• View the pulse-width-modulated (PWM) signal.

A. General Topics

Which of the following components would most likely cause the A/C compressor clutch to disengage?

• Restricted cabin air filter

• Transmission temperature

• Oxygen sensor temperature

• Temperature blend air door with stripped gears

A. General Topics

A vehicle with an automatic temperature control (ATC) system has excessive moisture on the inside of the windshield. After the concern is verified, which components or system should the technician investigate?

• Humidity sensor

• Sun load sensor

• Ambient air temperature sensor

• Blend door actuators

A. General Topics

If a technician is replacing an automatic temperature control (ATC) module, which test ensures the mode door stop positions are detected?

• The A/C Cool Down Test

• The A/C Performance Test

• The HVAC Actuator Calibration Test

• The Heater Performance Test

A. General Topics

vehicle is brought in with a poorly performing A/C system. No DTCs are set. The technician suspects the in-car temperature aspirator. What is the next logical diagnostic step to take?

• Check for a shorted aspirator thermistor sensor circuit.

• Check for an open aspirator thermistor sensor circuit.

• Measure the current draw of the aspirator motor.

• Inspect the aspirator for debris or dirt accumulation.