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100+ Free NATE AC Service Practice Questions

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2026 Statistics

Key Facts: NATE AC Service Exam

100

Practice Questions

OpenExamPrep

100

Exam Questions

NATE

2.5 hours

Time Limit

NATE

70%

Passing Score

NATE

Core required

Prerequisite Exam

NATE

$45

Retake Fee

NATE

The NATE Air Conditioning Service Specialty is a service- and diagnostics-focused HVAC certification from North American Technician Excellence (NATE). The specialty exam has 100 multiple-choice questions delivered over 2 hours 30 minutes, with a 70% passing score (70 of 100 correct). It is taken together with the required NATE Core Knowledge exam to earn the Professional-level certification, and NATE recommends roughly two years of field experience. Content emphasizes diagnostics and troubleshooting, refrigerant-circuit theory and components, electrical and controls, superheat/subcooling charging, and EPA Section 608 refrigerant recovery, all from a service technician's perspective (distinct from the AC Installation specialty). This free prep includes 100 research-based practice questions with explanations and an AI tutor.

Sample NATE AC Service Practice Questions

Try these sample questions to test your NATE AC Service exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In a residential air conditioning system, where does the refrigerant absorb heat from the conditioned space?
A.Condenser coil
B.Evaporator coil
C.Compressor discharge
D.Liquid line filter-drier
Explanation: The evaporator coil is the low-pressure, low-temperature side where liquid refrigerant boils and absorbs heat from the indoor air passing over it. This is the heat-absorption point of the refrigeration cycle.
2Which component of the refrigeration cycle changes high-pressure liquid into low-pressure liquid/vapor just before the evaporator?
A.Compressor
B.Condenser
C.Metering device
D.Accumulator
Explanation: The metering device (TXV, fixed orifice/piston, or capillary tube) creates the pressure drop that lowers refrigerant pressure and temperature before it enters the evaporator, producing a low-pressure liquid/flash-gas mixture.
3The four major components of the basic vapor-compression refrigeration cycle are the compressor, condenser, metering device, and:
A.Reversing valve
B.Evaporator
C.Receiver
D.Suction accumulator
Explanation: The four core components are the compressor, condenser, metering device, and evaporator. Together they move refrigerant through the four states of the cycle to absorb and reject heat.
4What is the term for the heat added to a vapor above its saturation (boiling) temperature at a given pressure?
A.Subcooling
B.Superheat
C.Latent heat
D.Sensible cooling
Explanation: Superheat is the number of degrees a vapor is heated above its saturation temperature at the existing pressure. On the evaporator/suction side it confirms all liquid has boiled to vapor before reaching the compressor.
5A system uses a fixed orifice (piston) metering device. Which measurement is the correct method to verify the refrigerant charge?
A.Subcooling
B.Total superheat using the manufacturer's charging chart
C.Condenser split only
D.Discharge line temperature
Explanation: Fixed-orifice systems are charged by total (suction) superheat compared to a target value from the manufacturer's charging chart, which is based on indoor wet-bulb and outdoor dry-bulb temperatures. The orifice does not control superheat, so superheat reflects charge.
6A system uses a thermostatic expansion valve (TXV). Which measurement is the correct method to verify the refrigerant charge?
A.Total superheat
B.Subcooling
C.Evaporator superheat only
D.Suction pressure alone
Explanation: On a TXV system, the valve maintains a relatively constant evaporator superheat regardless of charge, so superheat is not a reliable charge indicator. Subcooling, measured at the liquid line, is the correct method and is compared to the manufacturer's target (commonly around 10-18 degrees F).
7Subcooling is calculated by taking the saturated liquid temperature (from the P/T chart for the high-side pressure) and:
A.Adding the measured liquid line temperature
B.Subtracting the measured liquid line temperature
C.Subtracting the suction line temperature
D.Adding the outdoor ambient temperature
Explanation: Subcooling = saturated condensing temperature (converted from liquid/head pressure) minus the actual measured liquid line temperature. The result is how many degrees the liquid has been cooled below its condensing point.
8On an R-410A system the high-side gauge reads 365 psig and the P/T chart shows that pressure corresponds to a saturated temperature of about 110 degrees F. The liquid line measures 98 degrees F. What is the subcooling?
A.8 degrees F
B.12 degrees F
C.22 degrees F
D.98 degrees F
Explanation: Subcooling = saturated condensing temperature minus liquid line temperature = 110 - 98 = 12 degrees F. This falls within a typical 10-15 degree target, suggesting an acceptable charge on a TXV system.
9During service, you measure high superheat and low subcooling on a TXV system. What is the most likely cause?
A.Overcharge of refrigerant
B.Undercharge (low refrigerant)
C.Restricted condenser airflow
D.Oversized evaporator
Explanation: High superheat with low subcooling is the classic signature of an undercharged system: too little refrigerant means little liquid stacking in the condenser (low subcooling) and a starved evaporator (high superheat). Recover-and-weigh or add charge per the chart.
10A technician finds low suction pressure, high superheat, and low subcooling, but the metering device and airflow check out. What should be done next?
A.Add refrigerant per the manufacturer's method
B.Recover all refrigerant and replace the compressor
C.Increase blower speed only
D.Replace the condenser fan motor
Explanation: Low suction, high superheat, and low subcooling with normal airflow and a good metering device indicate an undercharge. The correct service action is to add refrigerant and verify charge by superheat (fixed orifice) or subcooling (TXV).

About the NATE AC Service Exam

The NATE Air Conditioning Service Specialty is a service- and troubleshooting-focused HVAC certification exam with 100 multiple-choice questions delivered over 2.5 hours, requiring 70% to pass. It validates a technician's ability to diagnose, charge, and repair residential air conditioning systems, and is taken alongside the required NATE Core exam to earn Professional certification.

Assessment

100 multiple-choice questions over 2 hours 30 minutes, 70% to pass; the Air Conditioning Service specialty is taken with the required NATE Core exam to earn Professional certification. This practice bank is 100 service-focused items.

Time Limit

2 hours 30 minutes

Passing Score

70%

Exam Fee

Varies by NATE testing organization (commonly ~$60-$160 per specialty exam); $45 retake (North American Technician Excellence (NATE))

NATE AC Service Exam Content Outline

15%

AC Theory & Refrigerant Flow

Vapor-compression cycle, P/T charts and saturation, R-410A vs R-22 pressures, latent and sensible heat, enthalpy, and oil return

18%

Components (Compressor, Condenser, Evaporator, Metering)

Scroll/reciprocating compressors, coils, TXV, fixed orifice, capillary tube, EEV, accumulator, filter-drier, sight glass, and crankcase heater

18%

Electrical & Controls

24V control circuits and thermostats, contactors, run/start capacitors, potential relays, PSC/ECM motors, pressure switches, and meter testing

25%

Diagnostics & Troubleshooting

Interpreting pressures, superheat and subcooling to find undercharge, overcharge, restrictions, dirty condensers, frozen coils, noncondensables, and compressor faults

14%

Superheat / Subcooling Charging

Charging fixed-orifice systems by superheat and TXV systems by subcooling, charging charts, wet-bulb/dry-bulb inputs, weigh-in, and variable-capacity modes

10%

Refrigerant Recovery & EPA 608

EPA Section 608 Type II rules, recovery vacuum levels, the venting prohibition, deep evacuation, nitrogen leak testing, reclaim/recycle, and cylinder safe fill

How to Pass the NATE AC Service Exam

What You Need to Know

  • Passing score: 70%
  • Assessment: 100 multiple-choice questions over 2 hours 30 minutes, 70% to pass; the Air Conditioning Service specialty is taken with the required NATE Core exam to earn Professional certification. This practice bank is 100 service-focused items.
  • Time limit: 2 hours 30 minutes
  • Exam fee: Varies by NATE testing organization (commonly ~$60-$160 per specialty exam); $45 retake

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

NATE AC Service Study Tips from Top Performers

1Weight your study toward diagnostics and troubleshooting plus charging, since interpreting pressures, superheat, and subcooling is the core of a service exam
2Memorize the charging rule: fixed-orifice systems are charged by superheat, TXV systems by subcooling, and know how to calculate each from the P/T chart
3Learn the classic fault signatures: high superheat plus low subcooling equals undercharge, while low superheat plus high subcooling equals overcharge
4Know R-410A's higher operating pressures and that gauges, hoses, and recovery gear must be rated for it; use the correct P/T chart
5Review EPA 608 Type II essentials: recovery vacuum levels, the venting prohibition, deep evacuation to about 500 microns, and 80% cylinder fill
6Complete all 100 practice questions and review every miss with the AI tutor before sitting the exam

Frequently Asked Questions

How many questions are on the NATE AC Service exam and how long is it?

The NATE Air Conditioning Service Specialty exam has 100 multiple-choice questions and you are allotted 2 hours and 30 minutes. You need 70% (70 of 100) to pass.

What score do I need to pass the NATE AC Service exam?

You need 70% to pass, which means answering at least 70 of the 100 questions correctly. The specialty is taken with the required NATE Core exam to earn the Professional-level certification.

Do I need the NATE Core exam before the AC Service specialty?

Yes. The Core Knowledge exam plus a service or installation specialty together earn the NATE Professional certification. NATE also recommends about two years of HVAC field experience before attempting a service-level specialty.

How is the AC Service specialty different from the AC Installation specialty?

The Service specialty emphasizes diagnosing and repairing existing systems, reading pressures and superheat/subcooling, troubleshooting electrical and refrigerant faults, and EPA 608 recovery. The Installation specialty focuses on sizing, setting, connecting, and starting up new equipment.

How much does the NATE AC Service exam cost?

Specialty exam pricing varies by the NATE-approved testing organization you use, commonly in the range of roughly $60-$160 per specialty exam. Retakes are $45 each. Contact your testing organization for exact local pricing.

Is this free NATE AC Service practice as good as paid prep?

Our 100 practice questions cover the same service-focused domains as the exam, with a teaching explanation for every answer plus free daily AI tutor interactions. All content is free forever and updated for 2026.