NAPA - National Automotive Parts Association Certified Mechanic Heating and Air Conditioning Questions and Answers

Question 1

A customer complains their vehicle's A/C blows cool air while driving at highway speeds but blows warm air when stopped in traffic or at idle. Which of the following is the MOST likely cause?

Accepted Answer

An inoperative radiator/condenser cooling fan

Answer

A faulty blend door actuator

Answer

A low refrigerant charge

Answer

A clogged orifice tube

Question 2

What are the two primary functions of a receiver/drier in an A/C system that uses an expansion valve?

Accepted Answer

To store refrigerant and remove moisture

Answer

To compress refrigerant and increase its pressure

Answer

To meter refrigerant flow and sense temperature

Answer

To cool the refrigerant and protect the compressor from liquid

Question 3

When servicing an A/C system containing R-1234yf refrigerant, which of the following is a critical difference compared to servicing an older R-134a system?

Accepted Answer

R-1234yf is mildly flammable and requires dedicated, certified service equipment.

Answer

R-1234yf operates at significantly higher pressures.

Answer

The system can be topped off with R-134a if needed.

Answer

R-1234yf does not require the use of specific lubricating oils.

Question 4

A vehicle's heater blows cold air, even when the engine is at full operating temperature. The technician confirms the coolant level is correct and feels the two heater hoses at the firewall. The inlet hose is hot, while the outlet hose is significantly cooler. What is the MOST likely cause?

Accepted Answer

A clogged or restricted heater core

Answer

A stuck-open thermostat

Answer

A faulty blend door actuator

Answer

An inoperative blower motor

Question 5

A technician connects a manifold gauge set to an A/C system and observes that both the static and running pressures on the high and low sides are significantly lower than normal for the ambient temperature. This reading is a classic indicator of:

Accepted Answer

A low refrigerant charge

Answer

An overcharged system

Answer

A restriction in the high side

Answer

A failing compressor

Question 6

In a vehicle with an Automatic Temperature Control (ATC) system, which sensor provides the primary input to the control module for maintaining the desired cabin temperature?

Accepted Answer

In-cabin temperature sensor

Answer

Ambient air temperature sensor

Answer

Sunload sensor

Answer

Evaporator temperature sensor

A customer complains their vehicle's A/C blows cool air while driving at highway speeds but blows warm air when stopped in traffic or at idle.Which of the following is the MOST likely cause?

A customer complains their vehicle's A/C blows cool air while driving at highway speeds but blows warm air when stopped in traffic or at idle.
Which of the following is the MOST likely cause?