ASE Practice Test (A7: Heating & Air Conditioning) 2

Question 1

An R-134a A/C system has low suction pressure (low side) and high discharge pressure (high side) during operation. Refrigerant charge is verified as correct. What is the MOST likely cause?

Accepted Answer

A restriction in the liquid line or expansion device

Answer

System is overcharged with refrigerant

Answer

Compressor suction valves are leaking

Answer

Condenser fan motor has failed

Question 2

A technician connects manifold gauges to an R-134a system and finds both high and low side pressures equalize to approximately 70 psi with the engine off and A/C off on an 80°F day. What does this indicate?

Accepted Answer

The system is at normal static pressure for R-134a at 80°F

Answer

Both pressures equalizing confirms a refrigerant leak somewhere in the system

Answer

The compressor has failed and cannot separate high and low side pressures

Answer

The system has moisture contamination causing pressure equalization

Question 3

When an R-134a A/C system is recovering refrigerant, the recovery machine indicates the system contained 0.8 lbs instead of the 1.4 lb specification on the underhood label. What should the technician do AFTER completing service?

Accepted Answer

Perform a leak test before recharging, then charge to specification weight

Answer

Charge the system to the specified weight and return the vehicle without leak testing

Answer

Charge the system with the recovered 0.8 lbs only, as adding more may overcharge

Answer

Recharge to 1.4 lbs, test the system, and note the discrepancy in the repair order

Question 4

A customer complains that the A/C blows warm air at idle but cools normally when driving at highway speeds. What is the MOST likely cause?

Accepted Answer

Condenser cooling fan not operating

Answer

Low refrigerant charge

Answer

Evaporator icing over at idle

Answer

Compressor clutch slipping at low RPM

Question 5

What refrigerant property makes the expansion valve (TXV) or orifice tube critical to A/C system operation?

Accepted Answer

They create the pressure drop that allows liquid refrigerant to evaporate and absorb heat

Answer

They allow only the correct amount of oil to circulate with the refrigerant

Answer

They filter moisture from the refrigerant before it enters the compressor

Answer

They control refrigerant temperature to prevent evaporator freezing

Question 6

A heater core is leaking coolant into the passenger compartment. The repair requires draining the cooling system. After the repair, the cooling system is refilled. What is the MOST important step to complete BEFORE checking for leaks?

Accepted Answer

Bleed the cooling system of trapped air

Answer

Road test the vehicle to operating temperature

Answer

Check the coolant reservoir level and cap condition

Answer

Run the engine at high RPM to pressurize the system quickly