Question 1: A technician measures high superheat and low subcooling on a fixed-orifice system with clean filters and good airflow. What is the most likely cause?
- Undercharge
- Overcharge
- A stuck contactor
- A dirty condenser coil
NATE_AC_SERVICE
NEC 2023
NATE AC Service Practice Test 10
This final review test mixes refrigerant diagnostics, airflow, electrical troubleshooting, and refrigerant handling into realistic field scenarios, pulling together everything from the earlier tests.
TOPICS COVERED
NATE AC Service
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Frequently Asked Questions
Yes — completely free with no signup required. Every question includes a full explanation of the correct answer.
Two: the NATE Core exam plus at least one specialty exam (for example AC Service, Heat Pump Service, or Air Distribution Service). You can take them on the same day or separately.
The Core exam has 50 questions and each installation or service specialty exam has 100 questions. You need 70% on each to pass — 35 of 50 on Core and 70 of 100 on a specialty. Check natex.org for the current format before you book.
NATE certification lasts two years. To renew, you submit 16 hours of continuing education or retake the specialty exam before your certification expires.
No. These are independent practice tests written to match the published NATE exam topics. They are not official NATE exam questions.
Exam Tip: Work through scenario questions step by step: rule out airflow first, then check refrigerant charge, then look at electrical components if pressures and airflow are normal.
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30 min
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NATE AC Service Practice Test 10 — Question List
Question 2: A technician measures low superheat and high subcooling on a fixed-orifice system with clean filters and good airflow. What is the most likely cause?
- A frozen evaporator coil caused by a dirty filter
- A failed condenser fan motor
- Overcharge
- A weak run capacitor
Question 3: A homeowner calls about ice on the indoor unit and weak airflow. After the coil thaws, what should the technician check first?
- Replace the compressor immediately
- Rewire the thermostat first
- Add refrigerant without checking anything else
- The air filter and general airflow
Question 4: A technician finds high head pressure and a compressor amp draw well above nameplate RLA. The condenser coil is caked with dirt. What should be done first?
- Clean the condenser coil, then re-check pressure and amp draw
- Replace the compressor without further checks
- Increase the refrigerant charge immediately
- Replace the thermostat
Question 5: A compressor hums, trips its overload, and the run capacitor tests within its normal microfarad range. What should the technician check next?
- The thermostat display backlight
- Whether the compressor is mechanically stuck or seized
- The contactor coil resistance
- The indoor air filter only
Question 6: A technician must add a large charge of R-410A after a repair and evacuation. What is the correct approach?
- Weigh liquid into the high side with the compressor off, then meter liquid slowly into the suction side
- Add liquid unrestricted into the suction side with the compressor running
- Draw vapor from the cylinder into the suction side for the entire charge
- Charge until the suction saturation temperature matches the outdoor temperature
Question 7: After brazing a repair on a leaking line, what must happen before the system is recharged with refrigerant?
- Nothing else is needed, charging can begin immediately
- The thermostat must be replaced
- The condenser fan must be replaced
- The system must be evacuated with a vacuum pump
Question 8: A technician is charging a TXV system and wants the most reliable single reading to judge overall refrigerant charge. Which should be used?
- Subcooling
- Indoor humidity
- Compressor amp draw only
- Thermostat cycle length
Question 9: A unit runs continuously with the thermostat set well above room temperature, and the technician measures 24V at the contactor coil at all times, even with the thermostat off. What does this suggest?
- The condenser fan capacitor is oversized
- The refrigerant charge is too high
- A wiring problem or stuck thermostat sending a constant call, not a stuck contactor
- The evaporator coil is dirty
Question 10: Before testing a dual run capacitor with a multimeter, what must the technician do first?
- Test it directly with power still on
- Turn off power and safely discharge the capacitor first
- Add refrigerant before testing electrical components
- Skip discharging since dual capacitors are always safe
Question 11: A technician accidentally connects an R-22-rated gauge set to an R-410A system. What is the main concern?
- There is no concern, all gauge sets work identically
- R-410A pressures are always lower, so this is not a safety issue
- The gauges will read in the wrong units
- R-410A operates at higher pressures, which the R-22-rated gauge set may not safely handle
Question 12: A technician thaws a frozen coil, confirms the filter and airflow are good, then finds low subcooling and high superheat. What is the most likely combined explanation?
- The system is undercharged, explaining both the icing and the readings
- The thermostat wiring caused the icing
- The condenser fan capacitor caused the icing
- The system is overcharged
Question 13: What is the general recommended order of diagnosis when a technician is unsure whether a problem is airflow-related or refrigerant-related?
- Always adjust refrigerant charge first, regardless of airflow
- Confirm airflow is normal first, then evaluate refrigerant charge
- Replace the compressor first in every case
- Airflow and refrigerant charge are unrelated and can be checked in any order with no consequence
Question 14: A technician checks the nameplate on an unfamiliar system and finds it uses R-32. What should change about the technician's approach compared to servicing a familiar R-410A system?
- Nothing should change, all refrigerants are handled identically
- R-32 can be vented legally in small amounts
- Follow A2L-specific safety practices since R-32 is mildly flammable
- R-32 requires no leak detection at all
Question 15: A technician reads a suction saturation temperature of 42 degrees F and a suction line temperature of 55 degrees F. What is the superheat, and is it within the general normal range for a fixed-orifice system?
- 97 degrees F, abnormally high
- 55 degrees F, abnormally high
- 3 degrees F, abnormally low
- 13 degrees F, within normal range
Question 16: A technician reads a condensing saturation temperature of 108 degrees F and a liquid line temperature of 96 degrees F. What is the subcooling, and is it within the general normal range?
- 12 degrees F, within normal range
- 204 degrees F, abnormally high
- 96 degrees F, abnormally high
- 12 degrees F, abnormally low
Question 17: While recovering a large refrigerant charge, why should a technician monitor the recovery cylinder weight on a scale throughout the process?
- To calculate the customer's final bill only
- To avoid overfilling the cylinder beyond its rated safe fill level
- Weight monitoring is not necessary during recovery
- To determine how much oil was removed
Question 18: A technician confirms the filter, coil, and ducts are all clean and correctly sized, but airflow is still below the rated CFM. The blower motor has multiple speed taps. What should be checked?
- The refrigerant type in the system
- The outdoor fan motor speed
- Whether the correct speed tap is wired for rated airflow
- The condenser fan capacitor rating
Question 19: A technician finds both a dirty condenser coil and a slightly low refrigerant charge on the same system. What is a sound approach?
- Add refrigerant first, then consider the coil later
- Ignore the dirty coil since it is a minor cosmetic issue
- Replace the whole system regardless of these findings
- Clean the condenser coil first, then re-evaluate refrigerant charge
Question 20: A technician finds high superheat and high (or normal) subcooling on a fixed-orifice system, with airflow confirmed normal. What does this pattern most likely indicate?
- A restriction, such as a clogged filter drier
- A simple undercharge only
- A dirty evaporator coil only
- A weak indoor blower capacitor only
Question 21: Before starting any electrical diagnostic work inside the outdoor unit, what two safety steps should a technician always follow?
- Add refrigerant first and check voltage last
- Verify power is off at the disconnect, and safely discharge capacitors
- Skip verification since the breaker label should be trusted completely
- Only discharge capacitors if the system is over ten years old
Question 22: On a new installation, the correct order is: pressure test with nitrogen, evacuate with a vacuum pump, then charge with refrigerant. Why does nitrogen testing come first?
- Because nitrogen must always be charged into the system permanently
- Because vacuum pumps cannot be used on new installations
- Because finding and repairing a leak first avoids wasting time on a system that will not hold vacuum
- Because refrigerant must always be added before any testing
Question 23: Which compressor type is most likely to be found in a modern residential split-system AC unit?
- Centrifugal compressor
- Screw compressor
- Axial compressor
- Scroll compressor
Question 24: A compressor with a history of hard starting is being upgraded from a PSC-only setup. What addition would help provide more starting torque?
- A hard start kit adding a start capacitor and relay
- A larger contactor with more poles
- A second condenser fan motor
- A bigger air filter
Question 25: A suspected leak is in a hard-to-reach spot behind the evaporator coil where soap bubbles cannot easily be applied. What method might work better in this situation?
- There is no alternative method available in this case
- An electronic leak detector, since its probe reaches tight spaces more easily
- A megohmmeter, which is used to test motor winding insulation, not leaks
- A manometer, which is used to measure duct static pressure, not leaks
Question 26: After a complex repair involving a leak fix, evacuation, and full recharge, what should the technician record on the service ticket?
- Nothing needs to be recorded once the repair is done
- Only the total invoice amount needs to be recorded
- Leak location/repair, vacuum level, refrigerant added, and final readings
- Only the technician's name and the date
Question 27: A "no cooling" call could stem from airflow, refrigerant charge, or electrical problems. What is a sound general diagnostic approach a technician should follow?
- Always replace the compressor first as a precaution
- Randomly guess at parts to replace without a system
- Skip airflow checks entirely and go straight to refrigerant charge
- Start with simple checks like airflow and power, then move to refrigerant diagnostics
Question 28: What should a technician always confirm before connecting a refrigerant cylinder to charge a system?
- That the cylinder refrigerant type matches the nameplate specification
- That the cylinder is a specific brand only
- That the cylinder is at least half full, so liquid can be drawn
- That the cylinder is completely full before starting
Question 29: A high-pressure switch trips repeatedly. The technician finds a clean condenser coil, a working fan, and correct refrigerant charge. What should be checked next?
- The indoor thermostat battery level
- Airflow clearance around the unit and possible recirculation of warm air
- The evaporator drain pan only
- The low-pressure switch setting
Question 30: A fixed-orifice system shows 25°F superheat and 18°F subcooling, with normal airflow and a 10°F temperature drop across the liquid-line filter drier. What is the most likely problem?
- A restricted liquid-line filter drier
- An overcharged system
- An undercharged system
- A failed condenser fan motor
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