20 Heating & Air Conditioning Practice Questions & Answers

1. 1. A customer reports that airflow from the dash vents has grown steadily weaker and that a musty smell appears when the fan is switched on. Inspection of the cabin air filter is part of the scheduled maintenance. What does a heavily loaded cabin air filter do to the HVAC system?

   • A.It forces the blower motor to run one speed faster than commanded.
   • B.It blocks the evaporator drain and pushes water onto the floor mat.
   • C.It restricts airflow through the case and can let the evaporator frost up.✓ Answer
   • D.It raises airflow at the floor vents while the panel vents stay normal.

   The cabin air filter sits upstream of the evaporator in the HVAC case, so a loaded element starves the blower of air. With too little air moving across the evaporator core, the core surface temperature falls to freezing and frost builds up, which restricts airflow even further; trapped damp debris in the media is what produces the musty odor.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: inspect and replace cabin air filterReport a problem with this question

2. 2. A technician replaces a cabin air filter as part of a maintenance service. Which practice is correct?

   • A.Install it so the airflow arrow points the way air moves through the case.✓ Answer
   • B.Fit it upside down so trapped debris falls out when the fan first starts.
   • C.Wash the old filter media and reinstall it if it is not visibly torn.
   • D.Install it with the pleats running parallel to the blower motor shaft for support.

   Cabin air filters are directional: the media layers, and any carbon layer, are built to filter in one direction only, and the arrow printed on the frame is referenced to the airflow direction through the case. Installed backwards the media loads unevenly and can shed captured debris downstream, and a washed element loses its structure and restricts airflow.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: inspect and replace cabin air filterReport a problem with this question

3. 3. A customer complains of a musty smell from the vents and a damp passenger-side carpet on an air-conditioned vehicle. Technician A says a plugged evaporator drain can leave condensate standing in the case, which produces the odor. Technician B says a plugged evaporator drain can let condensate spill out of the case onto the passenger floor. Who is right?

   • A.Both A and B✓ Answer
   • B.A only
   • C.Neither A nor B
   • D.B only

   The evaporator condenses moisture out of the air and the drain carries that water out through the floor pan. When the drain plugs, the water has nowhere to go: it stands in the bottom of the case where microbial growth creates the musty odor, and once the case fills the water overflows past the seal into the passenger footwell. Both statements describe the same blocked drain.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: inspect and clean evaporator drainsReport a problem with this question

4. 4. During an A/C performance check on a stationary vehicle, the technician must verify condenser (cooling) fan operation. Which observation confirms the fan is working as intended?

   • A.The fan stops as soon as the blower is switched to its highest speed.
   • B.The fan turns freely by hand with the engine off and the key removed.
   • C.The fan runs whenever the compressor clutch is engaged and A/C is on.✓ Answer
   • D.The fan runs only after the engine coolant reaches its highest reading.

   The condenser rejects heat to air moving across it, and at low vehicle speed there is no ram air, so the fan must be commanded on with the A/C request rather than by coolant temperature alone. Verifying that the fan comes on with compressor engagement is the check; a fan that only responds to a high coolant reading will let head pressure climb and cooling fall off in traffic.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including blower and condenser fanReport a problem with this question

5. 5. During an A/C performance check the technician inspects the condenser. Which finding is a restriction to airflow that must be corrected?

   • A.A trace of refrigerant oil found at the condenser inlet line fitting.
   • B.Coolant hoses routed along the side of the radiator support bracket.
   • C.A condenser mounted ahead of the radiator in the cooling airflow path.
   • D.A mat of insects and road grit packed into the fins across the face.✓ Answer

   The condenser can only reject heat in proportion to the air that passes through its fins, so debris packed into the face directly cuts cooling capacity and drives high-side pressure up. An oil trace at a fitting is a leak indication rather than an airflow problem, and a condenser positioned ahead of the radiator is the normal design.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: inspect A/C condenser for restricted air flowReport a problem with this question

6. 6. All of the following are acceptable when servicing a condenser that has matted debris and flattened fins EXCEPT:

   • A.Straightening flattened fins with a fin comb sized to the fin spacing.
   • B.Using a high-pressure washer wand very close to the condenser fins.✓ Answer
   • C.Removing the debris trapped between the condenser and the radiator core.
   • D.Rinsing the face with low-pressure water, working from the engine side out.

   Condenser fins are thin aluminum and a high-pressure stream held close will flatten or tear them, which permanently reduces the surface area available for heat transfer and makes the restriction worse than the debris did. Low-pressure rinsing from the engine side pushes debris back out the way it entered, and a correctly sized fin comb restores the fin passages.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: inspect A/C condenser for restricted air flowReport a problem with this question

7. 7. Before connecting service equipment to a vehicle's A/C system, the technician must identify the refrigerant type. Which statement is correct?

   • A.The refrigerant type can be read from the color of the compressor clutch.
   • B.The underhood label and the service fitting sizes identify the refrigerant.✓ Answer
   • C.One recovery machine works on all types if it is purged first.
   • D.Any refrigerant may be added as long as the correct oil goes in with it.

   Refrigerants are not interchangeable: each type uses its own lubricant, its own uniquely sized service couplers so equipment cannot be cross-connected, and its own dedicated recovery and recharge machine. The underhood label states the refrigerant the system was built for, and the fitting sizes on the vehicle confirm it before anything is connected.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: identify A/C refrigerant type; recover and recharge system per manufacturer's specificationsReport a problem with this question

8. 8. During a maintenance inspection the technician finds refrigerant oil weeping from the A/C compressor shaft seal area, and the repair will require opening the sealed system. What is the correct next step?

   • A.Open the line slowly at the fitting so the refrigerant escapes gradually.
   • B.Run the compressor until the low side drops, then unbolt the fitting.
   • C.Add refrigerant first so the leak can be traced with the system running.
   • D.Recover the refrigerant with certified equipment before opening a line.✓ Answer

   Motor vehicle refrigerant may never be released to the atmosphere; it has to be pulled into approved recovery equipment before any joint in the sealed system is broken. This is also the boundary where the work leaves routine maintenance, because recovery and recharge require equipment dedicated to that refrigerant and a technician certified to handle it.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - task: recover and recharge system per manufacturer's specifications; U.S. Clean Air Act prohibition on venting motor vehicle refrigerantReport a problem with this question

9. 9. A technician performs a visual leak inspection of the A/C system. Which finding is the strongest indication of a refrigerant leak at that point?

   • A.An oily film with dust stuck to it at a line fitting.✓ Answer
   • B.A loose insulation wrap on the suction line at the fender.
   • C.A drip of condensation under the car from the drain tube.
   • D.A frosted low-side line right after the compressor engages.

   Refrigerant circulates carrying the compressor lubricant with it, so refrigerant escaping through a joint or a seal carries oil out too. The oil stays behind at the leak point and collects road dust into a dark greasy ring, which is why an oily, dirt-laden residue at a fitting is the classic visual leak indicator. Condensation under the vehicle and brief frost on the low side are normal operation.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: visually check A/C components for signs of leaksReport a problem with this question

10. 10. A technician performs an A/C performance check. The service information specifies a center-vent temperature no higher than 45 F under the stated test conditions, and the vehicle produces 62 F. What should the technician do next?

    • A.Replace the compressor, since the vent temperature is above the spec.
    • B.Release the vehicle, since the vent air is cooler than outside air.
    • C.Add refrigerant until the vent temperature reaches the specified value.
    • D.Record the reading and inspect airflow, drive belt and visible leak points.✓ Answer

    A performance check is a comparison: the measured vent temperature is judged against the manufacturer's figure for the stated test conditions, and 62 F against a 45 F limit is a fail that must be recorded. The maintenance-level response is to work through the causes a light-repair technician owns - restricted condenser, loaded cabin filter, slipping compressor belt, visible leaks - rather than charging by feel or condemning a component.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including vent temperatureReport a problem with this question

11. 11. Technician A says compressor clutch engagement is verified by watching the clutch plate pull in and turn with the pulley when the A/C is switched on. Technician B says a clutch that will not engage should be forced in by prying the plate against the pulley while the engine runs. Who is right?

    • A.B only
    • B.Both A and B
    • C.Neither A nor B
    • D.A only✓ Answer

    Clutch engagement is verified visually: with the system commanded on, the clutch plate should snap in against the rotating pulley and turn with it, and it should release when the system is switched off. Prying at a clutch on a running engine puts hands into a moving belt drive and can bend the plate or damage the compressor snout, so it is never an accepted check or repair.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including compressor engagementReport a problem with this question

12. 12. The blower motor on a vehicle runs at its highest speed only, and no lower speed setting produces any airflow. Technician A says a plugged cabin air filter is the cause. Technician B says a plugged evaporator drain is the cause. Who is right?

    • A.Neither A nor B✓ Answer
    • B.Both A and B
    • C.A only
    • D.B only

    Neither part determines which fan speeds work. A blocked filter or drain reduces air volume or leaves water in the case, but they affect all speeds alike. The reduced speeds are produced by the blower resistor or the blower control module, and on most systems the highest speed bypasses that device entirely, which is exactly why high still works when the lower steps do not.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including blower operationReport a problem with this question

13. 13. As part of verifying HVAC operation, a technician cycles the mode selector and the temperature control through their full range. What should be verified?

    • A.Blower speed rises on its own each time a colder temperature is selected.
    • B.The compressor clutch stays engaged in every mode, floor heat included.
    • C.Air moves to the outlet selected and temperature changes with the setting.✓ Answer
    • D.Vent temperature holds constant while the mode doors travel between outlets.

    The mode doors route air to the selected outlets and the blend door proportions how much air passes through the heater core, so the two checks are that airflow actually moves to the outlet chosen and that vent temperature sweeps as the temperature control is moved. A blend door that will not move gives normal airflow with no temperature change, and a mode door that sticks leaves air at the wrong outlet.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including blend and mode door operationReport a problem with this question

14. 14. A technician verifies operation of the recirculation control. Which result indicates the recirculation door is doing its job?

    • A.The blower drops to its lowest speed when recirc is selected.
    • B.Outside air keeps entering so the windshield stays clear.
    • C.Air is drawn from inside the cabin instead of the outside inlet.✓ Answer
    • D.The compressor clutch disengages while recirculation is selected.

    The recirculation door's only job is to close off the fresh-air inlet and route cabin air back into the case, so verification is confirming that the intake source actually changes when the control is selected. Recirculation does not command blower speed or compressor operation, and if outside air keeps entering the door has not moved.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including mode door operationReport a problem with this question

15. 15. A customer says the heater blows cool air after the engine has reached operating temperature. Technician A says the cabin air filter should be replaced because it cannot pass warm air. Technician B says the engine coolant level and condition should be checked as part of the heater inspection. Who is right?

    • A.A only
    • B.B only✓ Answer
    • C.Neither A nor B
    • D.Both A and B

    The heater core is fed by engine coolant, so a low level or an air pocket leaves the core without hot coolant flowing through it and the vents blow cool even at full temperature setting; checking coolant level and condition is therefore a legitimate part of a heater complaint inspection. A cabin filter restricts how much air moves, not how warm that air becomes, so Technician A's reasoning is wrong.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation, including heater operationReport a problem with this question

16. 16. A technician inspecting heater hoses would replace a hose showing any of these conditions EXCEPT:

    • A.Cracks in the outer cover where the hose passes over a bracket.
    • B.Printed manufacturer markings that are still legible on the hose.✓ Answer
    • C.A soft, spongy section felt near the hose end when it is squeezed.
    • D.A swollen, oil-soaked area at the clamp that has taken a set.

    Printed markings are simply how the hose is identified and say nothing about its condition. The other three are failures of the rubber and its reinforcement: a soft spongy spot near the end means the layers have broken down internally where degradation begins, cracks at a contact point mean the cover has been worn through, and an oil-soaked swollen section has lost the strength to hold pressure.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: visually check components for signs of leaks; inspect hoses and fittingsReport a problem with this question

17. 17. A technician inspects the A/C refrigerant lines and hoses. Which finding is LEAST likely to require correction?

    • A.A line with its protective spring guard slid out of position.
    • B.A hose secured to the body with its factory clip and grommet.✓ Answer
    • C.A hose contacting the exhaust heat shield behind the engine.
    • D.A hose rubbing against a bracket where its clip is missing.

    A hose held by its factory clip and grommet is routed and retained exactly as designed, which is the condition the inspection is looking for. The other three all put the hose where it will be worn or cooked: rubbing on a bracket wears the cover until refrigerant escapes, a displaced spring guard leaves the bend unsupported, and contact with exhaust heat hardens and cracks the hose.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: visually check A/C components for signs of leaksReport a problem with this question

18. 18. The compressor drive belt is checked as part of an A/C maintenance service. Which statement is correct?

    • A.A belt is serviceable as long as it does not squeal on a cold start.
    • B.Belt tension is correct when the belt can be twisted a half turn by hand.
    • C.Belt condition and tension are compared to the manufacturer's spec.✓ Answer
    • D.A glazed belt can be restored by applying dressing to the rib side.

    Belt wear limits and tension values are set by the vehicle manufacturer and are checked with the specified method and gauge, not by ear or by feel. Absence of a squeal does not prove the belt still has enough rib depth to drive the compressor under load, and belt dressing only masks slip while attacking the belt material.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: check drive belt for wear and tension; adjust or replace as neededReport a problem with this question

19. 19. A customer reports intermittent loss of air conditioning on a vehicle with automatic climate control. Before beginning maintenance work, the technician should:

    • A.replace the climate control head, since the fault is intermittent.
    • B.disconnect the battery to reset the climate control module.
    • C.clear all stored codes so only new faults will appear later.
    • D.retrieve and record any stored HVAC trouble codes with a scan tool.✓ Answer

    An intermittent fault may not be present while the vehicle is in the bay, so the stored codes and the data captured with them are often the only record that the fault occurred at all. Retrieving and recording them comes first; clearing codes or pulling the battery erases that evidence along with other module memory, and replacing a control head without any recorded evidence guesses at the repair.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - retrieve and record diagnostic trouble codes (DTCs) as part of verifying system operationReport a problem with this question

20. 20. A customer states only that the air conditioning "doesn't work well." What should the technician do FIRST?

    • A.Operate the system as the customer does and confirm the concern.✓ Answer
    • B.Recover the refrigerant so the system can be weighed and refilled.
    • C.Replace the cabin air filter and return the vehicle to the customer.
    • D.Recharge the system, since a low charge is the usual cause.

    A vague complaint has to be turned into an observed, described condition before any service is performed, because "doesn't work well" can mean weak airflow, no cold air, cold on one side only, or a noise. Operating the system the way the customer does establishes what actually happens, which is what determines the correct maintenance procedure and gives a baseline to verify the repair against afterward.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) - Heating, Ventilation, and Air Conditioning task: verify HVAC operation; verify the customer concern before serviceReport a problem with this question

Practice questions based on the Test Specification and Task List published in the Official ASE Study Guide for the Automobile Maintenance and Light Repair (G1) test. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. ASE certification requires passing the test and documenting relevant work experience, and appropriate vocational training may count toward that experience — confirm current requirements with ASE before testing. No question here keys a manufacturer specification: torque values, clearances, pressures and capacities differ by vehicle, so any figure a question needs is given in the question itself, exactly as you would read it off a service manual on the job. About the ASE G1 test →