ASE A/C Exam

An A/C compressor high-pressure release valve discharges refrigerant at approximately:

475 psi (3,275 kPa)`

During an air conditioning performance test, the technician notices that the compressor outlet is hot. Technician A says this is a normal condition. Technician B says the air conditioning system is overcharged. Who is right?

A Only

Technician A says that evacuating an A/C system will remove air and moisture from the system. Technician B says that evacuating an A/C system will remove dirt particles from the system. Who is right?

A Only

A manifold gauge indicates a system has low discharge pressure. The MOST likely cause of this condition is:

A damaged compressor reed valve.

An air conditioning system with a variable displacement compressor has poor performance in high demand situations. All of these could be the cause EXCEPT:

A faulty low pressure switch (Only on FOT system)

A vehicle's air conditioner blows cold air at normal speeds, but warm air while sitting at stop lights. The LEAST likely cause of this condition is:

A frozen expansion valve

A vehicle's air conditioning performance is reduced at low speeds and stop lights, but cools at highway speeds. Which of these is MOST likely the cause of this condition?

A missing fan shroud

During an initial inspection, the technician notices that one line on the receiver drier is cooler than the other. This is caused by:

A restriction in the receiver drier.

A compressor clutch will not engage. During testing, the technician finds there is 14.2V and a good ground at the clutch coil connector. Which of these could be the cause?

An incorrect air gap

A blower motor operates only in high speed. Technician A says there could be a short in the motor's power feed. Technician B says it may have a faulty blower motor resistor. Who is correct?

B Only

The heater blows out only cold air at operating temperature. Technician A says a stuck closed thermostat could be the cause. Technician B says the cooling system could be low on coolant. Who is right?

B Only

Technician A says a fixed orifice tube varies the flow of refrigerant in relation to temperature. Technician B says a fixed orifice tube is located between the condenser and the evaporator. Who is correct?

B Only (A fixed orifice tube provides a consistent output, based upon the size of its orifice. It's a compromise between idle and highway conditions)

A gurgling sound is heard coming from inside the dashboard of a vehicle. Technician A says this is air trapped in the heater core. Technician B says this noise can be caused by a blown head gasket. Who is correct?

Both A and B

An EATC air conditioning system has low fan speed operation during high demand situations, like in direct sunlight. Technician A says this is because something is covering the sun load sensor's photo diode. Technician B says a sun load sensor is a variable resistor and can be tested with an ohmmeter. Who is correct?

Both A and B

An air conditioning system blows only warm air when the heater is on high output. Technician A says this could be a faulty heater control valve. Technician B says this could be caused by the cooling system's thermostat. Who is correct?

Both A and B

Technician A says a defective thermostat can cause the engine to operate at too cold of a temperature. Technician B says if the thermostat is stuck closed it can make a pinging or banging sound. Who is right?

Both A and B

Technician A says a radiator should always be inspected for leaks before installing a rebuilt engine. Technician B says overheating during slow in-town driving can be caused by an electric cooling fan fault. Who is right?

Both A and B

Technician A says all air conditioning connections use a gasket or O-ring to seal the system. Technician B says when replacing O-rings you lubricate the O-ring with the correct refrigerant oil to prevent nicks and ease installation. Who is right?

Both A and B

Technician A says refrigerant flows from the top of the condenser to the bottom. Technician B says a restriction in a condenser can cause damage to the compressor. Who is correct?

Both A and B

Technician A says the expansion valve is located on the inlet port of the evaporator. Technician B says the expansion valve's temperature sensing bulb is located near the outlet port of the evaporator. Who is correct?

Both A and B

Technician A says when the condenser airflow is restricted the pressure is high in both high and low lines. Technician B says an indication of low refrigerant is when both the high and low sides show low pressure. Who is right?

Both A and B

The carpet is wet on the passenger's side of a vehicle. Technician A says this may be caused by a leaking heater core. Technician B says this could be caused by a clogged evaporator case drain tube. Who is correct?

Both A and B

The compressor is rapidly cycling on and off on a CCOT (cycling clutch orifice tube) air conditioning system. Technician A says this condition can be caused by a low refrigerant charge. Technician B says this could be caused by a faulty clutch cycling switch. Who is correct?

Both A and B

The in-cabin temperature sensor is suspected for an air conditioner's poor performance. Technician A says the in-cabin temperature sensor is a NTC that should be tested for resistance with an ohmmeter. Technician B says the aspirator may be disconnected from the vent system. Who is correct?

Both A and B

Two technicians are discussing electric cooling fans and air conditioning performance. Technician A says electric fans regulate refrigerant temperatures more precisely than belt driven fans do. Technician B says electric cooling fans are controlled by control modules that use temperature and pressure actuated sensors and switches. Who is correct?

Both A and B

Using a DMM (digital multimeter), a technician measures 12 volts at the clutch coil, but it will not engage. Technician A says a bad clutch coil could be the cause. Technician B says a bad clutch coil ground could be the cause. Who is right?

Both A and B

What high-side and low-side pressure gauge readings would a technician find if the condenser fan were inoperative?

Both high-side high and low-side are high

Which of the following conditions is the MOST likely cause of a vehicle overheating?

Clogged radiator

All of the following issues regarding a receiver/dryer are correct, EXCEPT:

Evacuating system removes moisture from a saturated receiver/dryer

During a performance test on a CCOT system the manifold gauge indicates that the high side pressure is low and the low side pressure is high. This is caused by a:

Faulty compressor

A compressor clutch will not engage. Power and ground at the clutch coil are good. Which of the following is the MOST likely cause?

Incorrect air gap

An air conditioning system contains a thermostatic expansion valve. The suction line leading to the compressor is cool to the touch. This indicates:

Normal Condition

If a cooling system operates at too cool an operating temperature, the engine will do which of the following?

Produce higher emissions

All of the following tasks are performed when replacing an AC compressor, EXCEPT:

Reuse same compressor oil

A concern of intermittent AC cooling is being diagnosed. The gauge set shows intermittently high and low side pressure gauge readings and the high side intermittently drops to 100 psi. Which of the following is the MOST likely cause?

Stuck expansion valve

Technician A says while performing a retrofit from R-12 refrigerant to R134a refrigerant, the refrigerant must be recovered into a dedicated cylinder, they cannot be mixed. Technician B says R-12 refrigerant functions at higher pressures than R-134a refrigerant does. Who is correct?

Tech A

A frozen spot is noticed in the center of the condenser. Technician A says a frozen spot on a component or connection indicates a restriction in the system. Technician B says this is caused by a clogged orifice tube. Who is correct?

Tech A Only

A vehicle has poor air conditioning performance. The customer has added R134a refrigerant to the system. Technician A says to use a refrigerant identifier. Technician B says refrigerant mixtures are not recommended, but will not affect system pressures. Who is correct?

Tech A Only

During a visual inspection an oily spot is found on a hose leading from the compressor. Technician A says there may be a refrigerant leak in the system. Technician B says today's R134a systems use mineral oil instead of the older R12 compatible PAG oil. Who is correct?

Tech A Only

On a manual air conditioning system without automatic control, the compressor clutch does not operate. Technician A says there is a failed compressor thermal protector. Technician B says there is an incorrectly adjusted temperature door. Who is right?

Tech A Only

Technician A says a misadjusted temperature door could cause a poor heat complaint. Technician B says a defective resistor trio can cause a no high blower condition. Who is right?

Tech A Only

Technician A says the clutch relay protects the control head from the clutch circuit's high current. Technician B says open clutch relay windings result in compressor clutch engagement at all times. Who is correct?

Tech A Only

The owner of FOT system complains of poor cooling. Tech A says low refrigerant in the system. Tech B most likely cause is electrical short in wiring to the A/C compressor clutch

Tech A Only

Two technicians are discussing an inoperative electric blend door in an automatic air conditioning system. Technician A says to inspect the blend door's wiring and connections for an open circuit. Technician B says to troubleshoot this circuit with a test light. Who is correct?

Tech A Only

Technician A says an ambient temperature sensor senses cabin air temperature. Technician B says a faulty ambient temperature sensor can prevent compressor clutch engagement. Who is correct?

Tech B

A (TXV) thermostatic expansion valve system blows cold air for five minutes and then goes warm. Technician A says this condition is caused by a low refrigerant charge. Technician B says this condition is caused by moisture in the system. Who is correct?

Tech B Only

A compressor clutch coil is being tested. There is 12 volts at the connector and the ground is good. The resistance of the coil is 0.00 Ohms. Technician A says the coil has an open in it's windings. Technician B says the clutch coil has a short and has failed the resistance test. Who is correct?

Tech B Only

A technician is diagnosing a vehicle's air conditioning system. The vehicle has good engine performance, but the air conditioner is blowing warm air only. A yellow substance is noticed around the evaporator case drip tube. Technician A says this is coolant leaking from the heater core. Technician B says this is fluorescent dye leaking from the evaporator core. Which technician is MOST likely correct?

Tech B Only

Both the low and high pressures are within normal ranges, inside not cooling good. Tech A partially clogged FOT, Tech B too much refrigerant oil in system

Tech B Only

Frost is observed on the line between the condenser and the receiver-drier. Tech A this is normal operation on a hot and humid day. Tech B a restriction in the line or at the outlet of the condenser could be the cause.

Tech B Only

Two technicians are describing heater diagnosis. Technician A says one heater hose is hot to the touch and the other hose is cold when the heater core is functioning okay. Technician B says the upper radiator hose should be at engine operating temperature, which is very hot to the touch. Who is right?

Tech B Only

Two technicians are discussing a CCOT air conditioning system. Technician A says the system's pressure cycling clutch switch contains a bulb placed on the inlet port of the evaporator core. Technician B says a pressure cycling switch is located on the low side of the system. Who is correct?

Tech B Only

All these statements are true about a throttle position sensor EXCEPT:

The ECM disengages the A/C clutch at idle. (The compressor's clutch is not disengaged at idle, it's disengaged at WOT providing additional power when needed)

All of these are true about an air conditioner's evaporator EXCEPT:

The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.

All of the following statements are correct EXCEPT:

The throttle kicker is an electronic device that is typically part of the TP sensor.

All of these are true about an accumulator EXCEPT:

This system contains a thermostatic expansion valve to meter the refrigerant.

All of the following statements are correct regarding an air conditioning performance test, EXCEPT:

To avoid outside odor, operate AC System in RECIRC rather than FRESH mode.

All of the following are true regarding the expansion valve, EXCEPT:

When stuck closed, pressure on high side is low and pressure on low side is high.

All of the following statements about cooling system service are true EXCEPT:

When the cooling system pressure is increased, the boiling point is decreased

The high side pressure in an A/C system is above specs. Any of these could be the cause EXCEPT:

a broken compressor reed valve.

A customer complains about engine coolant loss. The cooling system is pressurized at 15 psi (103 kPa) for 15 minutes. There is no visible sign of coolant leaks in the engine or passenger compartments, but the pressure on the tester gauge decreases to 5 psi (34 kPa). This problem could be caused by any of the following defects EXCEPT:

a leaking heater core

On a vehicle with V-belts, an intermittent squealing noise is heard on acceleration with the A/C control switch in the on or off position. The most likely cause of this problem is:

a loose power steering belt

The vacuum valve in the radiator cap is stuck closed. The result of this problem could be:

an upper radiator hose collapsed after the engine was shut off

A port-fuel-injected engine has an excessively rich air:fuel ratio. This problem could be caused by:

the engine thermostat being stuck open