ASE A7 Heating and Air Conditioning Practice Test

25 practice questions

Choose an answer, then check it under Show answer.

1. Question 1 of 25Medium

   A vehicle's lower radiator hose collapses when the engine is revved. Which of these is LEAST likely to cause this condition?

   1. AA. A severe internal restriction in the radiator core tubes
   2. BB. A missing or corroded internal wire reinforcement spring
   3. CC. A thermostat that is stuck fully open
   4. DD. Internal delamination of the lower hose lining
   Show answer to question 1

   Answer: C. A thermostat that is stuck fully open

   A stuck-open thermostat allows continuous coolant flow and does not generate excessive suction in the lower radiator hose. The lower hose is on the suction side of the water pump, so a missing internal support spring, delaminated inner liner, or plugged radiator core will cause the pump to draw high vacuum and collapse the hose at higher engine speeds.

2. Question 2 of 25Medium

   A technician must recover refrigerant from a system of unknown service history, and the recovery cylinder will be shared with refrigerant from other jobs. What is the correct step before recovery begins?

   1. AA. Compare the system's high-side pressure with the pressure-temperature chart
   2. BB. Check the refrigerant for color and odor at the service port
   3. CC. Verify refrigerant type by whether the service fittings are quick-couple or threaded
   4. DD. Sample the system charge with a refrigerant identifier to check for contamination
   Show answer to question 2

   Answer: D. Sample the system charge with a refrigerant identifier to check for contamination

   A refrigerant identifier is the only reliable way to detect mixed refrigerants, flammable hydrocarbons, and excessive air before the charge is put into a shared recovery cylinder where it would contaminate the whole batch. Pressure alone cannot distinguish refrigerants clearly, and refrigerant has no dependable color or odor. Service fitting type only shows what the system was built or converted for, not what is actually in it.

3. Question 3 of 25Easy

   All of the following are functions of the expansion valve in an A/C system EXCEPT:

   1. AA. Metering refrigerant flow into the evaporator
   2. BB. Regulating superheat at the evaporator outlet
   3. CC. Removing moisture and contaminants from the refrigerant
   4. DD. Reducing refrigerant pressure so it boils at a low temperature
   Show answer to question 3

   Answer: C. Removing moisture and contaminants from the refrigerant

   Moisture and contaminants are removed by the filter-drier (receiver-drier), not by the expansion valve. The valve meters refrigerant into the evaporator, drops its pressure so it boils at a low temperature, and regulates superheat.

4. Question 4 of 25Medium

   A technician is replacing individual A/C components following a front-end collision. All of the following are appropriate procedures for adjusting system lubricant levels EXCEPT:

   1. AA. Adding the total system oil capacity directly into the new replacement evaporator core.
   2. BB. Adding the specified amount of clean oil when replacing the receiver-drier or accumulator.
   3. CC. Pouring a small specified amount of oil into new lines if significant oil was lost during rupture.
   4. DD. Adding the vehicle manufacturer's specified oil increment when replacing the condenser.
   Show answer to question 4

   Answer: A. Adding the total system oil capacity directly into the new replacement evaporator core.

   Adding the entire system oil capacity when only replacing an evaporator will severely overfill the system, because substantial oil remains distributed in the compressor, condenser, lines, and accumulator. Technicians should only add the specific component allowance (typically 1 to 3 ounces depending on OEM specification) unless the entire system has been completely flushed.

5. Question 5 of 25Medium

   With the mode selector set to panel, there is no vacuum at the panel mode actuator. Vacuum is present at the control head supply port, and the actuator moves the door when vacuum is applied directly. What should the technician check next?

   1. AA. The blower motor operation
   2. BB. The actuator diaphragm for leaks
   3. CC. Vacuum at the selector switch panel output
   4. DD. The refrigerant pressure
   Show answer to question 5

   Answer: C. Vacuum at the selector switch panel output

   The actuator works with direct vacuum, so the next step is to determine whether the selector switch is sending vacuum to the panel port. Checking the actuator diaphragm again is unnecessary because it already moved when vacuum was applied, and blower or refrigerant checks do not address the missing vacuum signal.

6. Question 6 of 25Easy

   A vehicle overheats at idle with the A/C on. A technician finds that the 40-amp cooling fan fuse is blown. The technician installs a new fuse, commands the fan on with a scan tool, and the fuse blows again immediately. With the fan motor connector disconnected, the fuse no longer blows and battery voltage is present at the fan B+ terminal in the connector. Which of these is the MOST likely cause?

   1. AA. High resistance in the cooling fan ground circuit
   2. BB. An open cooling fan dropping resistor
   3. CC. A shorted cooling fan relay coil winding
   4. DD. A seized or internally shorted cooling fan motor
   Show answer to question 6

   Answer: D. A seized or internally shorted cooling fan motor

   The fuse only blows with the motor connected, so the excessive current is flowing through the motor circuit itself; a seized or internally shorted motor draws far more current than the fuse rating. A shorted relay coil or high ground resistance would not blow the fuse in the motor feed, and an open dropping resistor would reduce or stop motor current rather than increase it.

7. Question 7 of 25Medium

   A ventilated seat does not cool the occupant. The thermoelectric device under the seat becomes cold on its upper side, the heat-sink fan under the seat runs, and current draw at the device is within the manufacturer's specification. No air moves through the seat cushion perforations. Which of these is the MOST likely cause?

   1. AA. The seat heater element is shorted
   2. BB. The seat ventilation blower is inoperative
   3. CC. The polarity at the thermoelectric device is reversed
   4. DD. The thermoelectric device is open internally
   Show answer to question 7

   Answer: B. The seat ventilation blower is inoperative

   The device is producing cold and drawing normal current, so the missing piece is the airflow that carries the cooled air through the cushion. Reversed polarity would make the seat side warm instead of cold, and an open device would draw no current.

8. Question 8 of 25Medium

   All of the following are correct steps when replacing a heater core EXCEPT:

   1. AA. Verifying the replacement core matches the original before installation
   2. BB. Checking the heater hoses and clamps for hardening or seepage
   3. CC. Inspecting the blend door and its actuator while the case is accessible
   4. DD. Reusing the original O-rings and seals if they still look serviceable
   Show answer to question 8

   Answer: D. Reusing the original O-rings and seals if they still look serviceable

   New seals and O-rings should be installed with a replacement heater core, because old seals harden and take a set and often seep after being disturbed. Inspecting the doors and actuator, checking the hoses and confirming the correct core all help prevent a repeat repair.

9. Question 9 of 25Medium

   A technician is reinstalling the instrument panel after replacing a leaking evaporator core. Which safety precaution should the technician follow when reconnecting the battery to re-enable the supplemental restraint system (SRS)?

   1. AA. Place a heavy weight on the passenger seat cushion to calibrate the occupant detection sensor.
   2. BB. Ensure no personnel are inside the vehicle and remain clear of the airbag deployment path.
   3. CC. Connect the negative battery terminal first while an assistant depresses the brake pedal.
   4. DD. Sit in the driver seat and hold the steering wheel firmly while turning the ignition on.
   Show answer to question 9

   Answer: B. Ensure no personnel are inside the vehicle and remain clear of the airbag deployment path.

   When reconnecting the battery to enable the SRS following interior service, all personnel must be outside the vehicle and clear of the trajectory of all airbags in the unlikely event of an accidental deployment. Sitting inside the vehicle in front of an airbag module creates an extreme hazard. Proper battery reconnection sequence requires attaching the positive cable first and the negative cable last to prevent accidental grounding shorts.

10. Question 10 of 25Medium

    A technician has evacuated a system for 30 minutes. The manifold gauge reads 29.9 inHg, but the technician is not sure the system is below 500 microns. What should the technician do?

    1. AA. Continue evacuating for another 30 minutes.
    2. BB. Charge the system; 29.9 inHg is sufficient.
    3. CC. Use a micron gauge to measure the vacuum level accurately.
    4. DD. Close the low-side valve and watch the high-side gauge.
    Show answer to question 10

    Answer: C. Use a micron gauge to measure the vacuum level accurately.

    A manifold gauge cannot accurately resolve deep vacuum levels near 500 microns, so a micron gauge is needed. Continuing to evacuate without an accurate measurement does not confirm that the system is ready to charge.

11. Question 11 of 25Medium

    While an ATC actuator calibration is running, which of these should the technician do?

    1. AA. Leave the doors free to travel and keep hands clear.
    2. BB. Set the blower to its highest speed.
    3. CC. Hold the blend door at the full-hot position.
    4. DD. Unplug the actuator feedback connector.
    Show answer to question 11

    Answer: A. Leave the doors free to travel and keep hands clear.

    The calibration procedure drives the doors through their full travel to learn the endpoints, so the doors must move freely without being forced by hand. Holding a door, disconnecting feedback, or forcing blower speed can interfere with the learned positions.

12. Question 12 of 25Medium

    All of the following are correct when refilling a cooling system EXCEPT:

    1. AA. Filling the expansion tank above its full mark
    2. BB. Using vacuum filling equipment when the manufacturer recommends it
    3. CC. Filling at the specified rate to let trapped air escape
    4. DD. Opening bleed screws as directed during the fill
    Show answer to question 12

    Answer: A. Filling the expansion tank above its full mark

    The expansion tank must have room for coolant expansion, so it should be filled only to the specified hot or cold mark. Filling at the specified rate and opening bleed screws as directed help prevent trapped air.

13. Question 13 of 25Easy

    All of the following statements regarding refrigerant recovery cylinders are correct EXCEPT:

    1. AA. Refillable recovery tanks must be hydrostatically retested every five years.
    2. BB. Refillable recovery tanks must not be filled past 80 percent of their rated capacity.
    3. CC. Disposable DOT-39 refrigerant cylinders may be reused to store recovered refrigerant.
    4. DD. Dedicated recovery cylinders are painted with a yellow top and a gray body.
    Show answer to question 13

    Answer: C. Disposable DOT-39 refrigerant cylinders may be reused to store recovered refrigerant.

    Disposable DOT-39 cylinders are designed strictly for one-time use and lack the structural integrity and relief mechanisms required for multiple cycles; federal regulations prohibit refilling them with recovered refrigerant. Dedicated recovery tanks must feature a gray body with a yellow top and must never exceed an 80 percent fill level to allow room for thermal expansion.

14. Question 14 of 25Medium

    An A/C compressor clutch engages and cools normally when first started, but disengages after 30 minutes of driving and fails to re-engage until the engine cools down. When the failure occurs, battery voltage and ground are confirmed at the clutch coil connector. Feeler gauge measurement reveals a clutch air gap of 0.055 in (1.4 mm), which is beyond specification. What is the correct repair procedure?

    1. AA. Remove shims from behind the clutch hub.
    2. BB. Install additional shims behind the clutch hub.
    3. CC. Replace the compressor pulley bearing.
    4. DD. Replace the electronic displacement control valve.
    Show answer to question 14

    Answer: A. Remove shims from behind the clutch hub.

    As the field coil gets hot, its internal electrical resistance increases, which weakens its magnetic strength. An excessive air gap may allow engagement when the coil is cold, but the weakened hot coil cannot pull the armature plate across the wide gap. Removing selective shims decreases the air gap to the manufacturer's specified tolerance, restoring reliable hot engagement.

15. Question 15 of 25Easy

    A customer states that the blower motor in a vehicle with a manual HVAC control head runs only when the blower switch is in the HIGH position. Which of these is the MOST likely cause?

    1. AA. An open ground circuit at the blower motor connector
    2. BB. An open circuit in the blower motor resistor assembly
    3. CC. A shorted coil in the blower motor relay
    4. DD. A blower motor that draws excessive current
    Show answer to question 15

    Answer: B. An open circuit in the blower motor resistor assembly

    In a manual system every speed except HIGH routes current through the blower motor resistor, while HIGH feeds the motor directly, so an open resistor allows operation on HIGH only. An open ground at the motor connector would stop the motor on every speed, including HIGH.

16. Question 16 of 25Easy

    A cooling fan circuit schematic shows a conventional relay with terminals 30, 85, 86, and 87. All of the following statements about reading this schematic are true EXCEPT:

    1. AA. Terminal 30 is the relay contact power feed from the fuse.
    2. BB. Terminals 85 and 86 are the relay coil connections.
    3. CC. Terminal 87 is the switched output to the cooling fan.
    4. DD. Terminal 30 is the relay coil control terminal.
    Show answer to question 16

    Answer: D. Terminal 30 is the relay coil control terminal.

    In a conventional relay schematic, terminal 30 is the contact power feed, terminals 85 and 86 are the coil connections, and terminal 87 is the switched output. Terminal 30 is not the coil control terminal; the coil is controlled through terminals 85 and 86.

17. Question 17 of 25Hard

    An electric blend door actuator works normally most of the time but stops intermittently, especially on rough roads. Technician A says a voltage drop test on the actuator power and ground circuits while the actuator is operating can reveal a poor connection. Technician B says wiggling the harness and connector while watching actuator operation on the scan tool can locate the intermittent circuit. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 17

    Answer: C. Both A and B

    Voltage drop testing under load finds excessive resistance in the power or ground side that a static voltage check would miss, and flexing the harness while monitoring actuator response reproduces the fault and isolates the affected circuit. Both methods are appropriate for an intermittent actuator complaint.

18. Question 18 of 25Easy

    An A/C compressor suffered a catastrophic internal mechanical failure that distributed metal debris throughout the high side of the system. Why must the discharge line assembly with an integral muffler be replaced rather than reverse-flushed?

    1. AA. The muffler contains a desiccant filter core that breaks down when exposed to flushing solvents.
    2. BB. Liquid flushing solvents chemically dissolve the synthetic nylon barrier layer inside the flexible hose.
    3. CC. High-pressure flushing solvent will distort the internal reed valves located inside the muffler housing.
    4. DD. The internal baffles and expansion chambers of the muffler trap debris that flushing cannot remove.
    Show answer to question 18

    Answer: D. The internal baffles and expansion chambers of the muffler trap debris that flushing cannot remove.

    A/C mufflers contain internal baffles, chambers, and expansion spaces designed to cancel pressure pulsations, but these cavities easily trap metallic debris that cannot be reliably purged by flushing, which risks contaminating the new compressor. Approved A/C flushing solvents are compatible with barrier hose materials and will not dissolve the nylon liner. Mufflers do not contain internal reed valves or desiccant filter cores.

19. Question 19 of 25Easy

    All of the following are correct when using a DSO to check a pulse-width-modulated blower motor control signal EXCEPT:

    1. AA. The signal should stay at a fixed duty cycle at all speeds.
    2. BB. The waveform should have clean transitions between high and low.
    3. CC. The duty cycle should change as blower speed is commanded.
    4. DD. Rounded or clipped transitions can indicate a circuit or driver fault.
    Show answer to question 19

    Answer: A. The signal should stay at a fixed duty cycle at all speeds.

    A pulse-width-modulated blower control signal changes duty cycle as blower speed is commanded, so a fixed duty cycle at all speeds is not normal. Clean transitions are expected, and rounded or clipped transitions can indicate a circuit or driver problem.

20. Question 20 of 25Hard

    A customer complains that the air conditioning does not blow cold air from the dash vents. The scan tool shows DTC B0413 (Temperature Control 1 Circuit Range/Performance). When monitoring live data, the blend door commanded position changes from 0% to 100% as the temperature dial is rotated, but the blend door actual position PID stays fixed at 50%. Technician A says the fixed 50% actual position PID indicates the blend door actuator motor is receiving normal battery voltage. Technician B says if the commanded position changes on the scan tool, the HVAC control head temperature knob potentiometer must be faulty. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 20

    Answer: D. Neither A nor B

    Neither technician is correct. Technician A is incorrect because the actual position PID reflects feedback potentiometer voltage or a default substitute value from the module, not actuator motor feed voltage. Technician B is incorrect because the commanded position PID changing in response to the knob confirms that the module is successfully reading the temperature knob potentiometer input.

21. Question 21 of 25Hard

    A technician flushes an evaporator core using an approved liquid flushing solvent. If the solvent is NOT thoroughly purged with dry nitrogen before reassembling and charging the system, what is the MOST likely result?

    1. AA. The solvent will react with desiccant to cause high low-side pressure.
    2. BB. The solvent will dilute the oil and cause compressor failure.
    3. CC. The solvent will freeze solid and plug the metering device.
    4. DD. The solvent will raise high-side pressure by creating non-condensable gas.
    Show answer to question 21

    Answer: B. The solvent will dilute the oil and cause compressor failure.

    Flushing solvents are formulated to dissolve and strip oil from internal metal surfaces. If solvent remains in the evaporator, it will mix with the new lubricant, stripping its viscosity and lubricity, which leads to rapid failure of the replacement compressor.

22. Question 22 of 25Hard

    A driver reports that pressing the defrost button sometimes selects floor mode, and pressing the mode button sometimes changes the temperature setting. Which of these is LEAST likely to cause this complaint?

    1. AA. Worn blower motor brushes
    2. BB. Contamination bridging adjacent switch contacts on the control board
    3. CC. Pinched or misrouted switch matrix ribbon cable
    4. DD. Incorrect control head installed or configured for the vehicle
    Show answer to question 22

    Answer: A. Worn blower motor brushes

    Wrong functions from button presses suggest cross-talk in the switch matrix, damaged ribbon cable wiring, or a control head with the wrong configuration. Worn blower motor brushes affect blower motor operation and do not change which HVAC function a button requests.

23. Question 23 of 25Hard

    All of the following sensor or electrical faults can prevent an automatic climate control system from properly clearing windshield fog EXCEPT:

    1. AA. An evaporator temperature sensor biased low to indicate 28°F (-2°C)
    2. BB. A cabin humidity sensor biased to indicate maximum relative humidity
    3. CC. An open ambient air temperature sensor circuit reading -40°F (-40°C)
    4. DD. A shorted mode door actuator signal circuit holding the door on floor mode
    Show answer to question 23

    Answer: B. A cabin humidity sensor biased to indicate maximum relative humidity

    A cabin humidity sensor biased high signals the climate control module that humidity is elevated, prompting the module to actively engage the A/C compressor and switch to fresh air mode to clear the glass. An evaporator temperature sensor falsely indicating below freezing causes the module to shut off the compressor to prevent icing, disabling dehumidification. An ambient temperature sensor reading extreme cold also locks out compressor operation, while a mode door stuck on floor prevents airflow from reaching the windshield.

24. Question 24 of 25Hard

    A vehicle uses a cable-operated temperature blend door. The door reaches full hot when the control lever is moved only partway, and full cold cannot be obtained. Which of these is the MOST likely cause?

    1. AA. A low refrigerant charge
    2. BB. Cable misadjustment or linkage indexing
    3. CC. A restricted heater core
    4. DD. A weak blower motor
    Show answer to question 24

    Answer: B. Cable misadjustment or linkage indexing

    The lever travel and door travel do not match, which indicates the cable is misadjusted or the door linkage is indexed incorrectly on its shaft. A restricted heater core would affect heat output, and refrigerant charge or blower strength would not change the mechanical relationship between the lever and the blend door.

25. Question 25 of 25Hard

    A technician is replacing the desiccant cartridge inside the integral receiver/drier of a subcooling condenser. Which of these is the correct procedure when installing the new desiccant?

    1. AA. Apply thread locking compound to the sealing plug threads to ensure a leak-free seal
    2. BB. Pre-saturate the new desiccant cartridge in fresh compressor oil before sliding it into the cavity
    3. CC. Install the desiccant immediately after removing it from its sealed bag and replace the plug O-ring
    4. DD. Bake the desiccant cartridge in an oven at 200 degrees Fahrenheit prior to installation
    Show answer to question 25

    Answer: C. Install the desiccant immediately after removing it from its sealed bag and replace the plug O-ring

    Desiccant bags must remain in their sealed moisture-proof packaging until immediately prior to installation to prevent absorbing atmospheric moisture, and the sealing plug O-ring must be replaced and lubricated with clean refrigerant oil. Pre-saturating the desiccant in oil reduces its surface area and moisture absorption capacity. Baking new desiccant is unnecessary and can damage modern plastic cartridges, and thread locker must not be used on refrigeration seals.

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