Previous NATE AC Service Practice Test 9

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.

30

Questions

30 min

Time

70%

Pass

Timer starts immediately. Progress is auto-saved.

NATE AC Service Practice Test 10 — Question List

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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 condenser fan blade color
The indoor air filter only

NEC Reference: NULL

Question 6: A technician needs to add a large amount of refrigerant to a system after a major repair. What is the correct and safe method?

Add liquid refrigerant to the low side while the compressor runs
Guess the charge amount based on outdoor temperature alone
Liquid charge into the high side with compressor off, then fine-tune with vapor
Vent refrigerant into the room to check for odor first

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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 refrigerant color will change permanently
R-410A operates at higher pressures, which the R-22-rated gauge set may not safely handle

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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
Only the color of the gauges needs to change
Follow A2L-specific safety practices since R-32 is mildly flammable
R-32 requires no leak detection at all

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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 the refrigerant's color

NEC Reference: NULL

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 thermostat display brightness
Whether the correct speed tap is wired for rated airflow
The condenser fan capacitor rating

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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

NEC Reference: NULL

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 painted a specific color, regardless of label
That the cylinder is completely full before starting

NEC Reference: NULL

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 color of the refrigerant lines

NEC Reference: NULL

Question 30: Which approach best reflects sound AC service diagnostic practice overall?

Skip systematic diagnosis and replace parts at random
Ignore safety steps when short on time
Work through airflow, charge, and electrical checks logically, using superheat/subcooling and safe practices
Only ever check one possible cause per service call

NEC Reference: NULL

EXAM CARD NATE_AC_SERVICE

Questions30

Time limit30 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)