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NATE_AC_SERVICE NEC 2023

NATE AC Service Practice Test 5

This test covers airflow diagnostics on the indoor side of AC systems, including dirty filters, dirty evaporator coils, blower problems, and frozen coil troubleshooting.

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: Never run a system with a badly iced evaporator coil. Turn off cooling, let the coil thaw or run fan-only, then find the root cause.

30

Questions

30 min

Time

70%

Pass

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NATE AC Service Practice Test 5 — Question List

Question 1: Why is proper airflow across the evaporator coil important?

It is critical for heat transfer, pressures, and superheat control
Airflow only matters for the condenser, not the evaporator
Airflow has no effect on refrigerant pressures
Airflow only matters in heating mode

NEC Reference: NULL

Question 2: What is a common effect of a badly clogged air filter on system operation?

Reduced airflow, leading to low suction pressure and possible frozen coil
It always raises head pressure on the condenser directly
It improves compressor efficiency
It has no measurable effect on the system

NEC Reference: NULL

Question 3: What are common causes of a frozen (iced) evaporator coil?

Low charge, restricted airflow, or a failing metering device
Overcharge is the only possible cause
A high SEER rating always causes coil icing
Excess outdoor temperature is the only cause

NEC Reference: NULL

Question 4: True or False: A technician should never continue running the cooling mode on a system with a significantly iced evaporator coil.

False, running cooling continuously will melt the ice faster
False, icing is not a real concern for compressors
True
False, only outdoor coils need to be thawed before running

NEC Reference: NULL

Question 5: What is the correct first step when a technician finds a badly frozen evaporator coil?

Turn off cooling and let the coil thaw, using fan-only if needed
Immediately add refrigerant to melt the ice faster
Increase the blower speed to maximum with cooling still running
Chip the ice off with a metal tool while the system runs

NEC Reference: NULL

Question 6: A technician replaces a dirty filter but airflow is still low. What should be checked next?

The thermostat battery level
The outdoor disconnect switch
The evaporator coil for dirt buildup
The refrigerant color

NEC Reference: NULL

Question 7: How can a dirty blower wheel reduce system airflow?

Dirt buildup disrupts airflow and reduces the wheel's efficiency
A dirty blower wheel always increases airflow
It has no effect on airflow, only on noise
It only affects heating mode operation

NEC Reference: NULL

Question 8: How can undersized return or supply ductwork affect a system?

It always increases airflow beyond design specs
It has no effect since ductwork size does not matter
It restricts airflow, causing symptoms like low suction pressure and coil icing
It only affects the outdoor unit, never the indoor coil

NEC Reference: NULL

Question 9: A technician finds high superheat, normal subcooling, and a clogged air filter. What is the most likely explanation?

The system is overcharged and needs refrigerant removed
The condenser fan motor has failed
The thermostat is miscalibrated
Restricted airflow from the dirty filter is starving evaporator heat transfer

NEC Reference: NULL

Question 10: True or False: Reduced airflow across the evaporator coil generally causes suction pressure to drop.

False, reduced airflow always raises suction pressure
False, airflow has no relationship to suction pressure
False, this only applies to fixed-orifice systems
True

NEC Reference: NULL

Question 11: What tool is used to measure duct static pressure to help diagnose airflow restrictions?

A manometer
A megohmmeter
A combustion analyzer
A refrigerant scale

NEC Reference: NULL

Question 12: On a belt-driven blower, what symptom might a slipping or worn belt cause?

Increased airflow beyond design specification
No possible effect on airflow
Immediate compressor failure
Reduced blower speed and airflow, sometimes with squealing

NEC Reference: NULL

Question 13: A homeowner has closed several supply registers to "save energy" in unused rooms. How can this affect the system?

It always increases refrigerant charge automatically
It has no effect on airflow or static pressure
It can restrict airflow and raise static pressure, similar to a dirty filter
It only affects the outdoor condenser fan

NEC Reference: NULL

Question 14: A homeowner reports weak airflow from all the vents. What is a logical first step for the technician?

Replace the compressor immediately
Rewire the thermostat
Add refrigerant without further checks
Check the air filter for dirt or blockage

NEC Reference: NULL

Question 15: True or False: Frost or ice seen on the suction line at the outdoor unit can be a sign of a frozen evaporator coil problem happening indoors.

False, the suction line is never affected by evaporator icing
False, frost on the suction line only means normal operation
False, only the liquid line shows signs of evaporator problems
True

NEC Reference: NULL

Question 16: A technician finds standing water and a clogged condensate drain near the indoor unit, along with reduced airflow. What is the most likely connection?

The two problems are always unrelated
A dirty coil can restrict airflow and contribute to drain clogging
The condenser fan capacitor caused both issues
The thermostat wiring caused both issues

NEC Reference: NULL

Question 17: Why do many manufacturers recommend checking or replacing air filters on a regular schedule, such as monthly to quarterly depending on filter type?

Filters never need to be checked once installed
It prevents airflow restriction that can reduce efficiency and cause icing
It has no effect on system performance at all
It only matters for commercial buildings

NEC Reference: NULL

Question 18: A homeowner installs a very high-efficiency filter (very fine media) not originally specified for the system. What is a possible risk?

It always improves airflow with no downside
It has no possible effect on system airflow
The denser media can create excess resistance and restrict airflow
It automatically increases refrigerant charge needs

NEC Reference: NULL

Question 19: Why should a technician verify proper airflow before making refrigerant charge adjustments based on superheat and subcooling readings?

Airflow problems can mimic charge problems, causing incorrect charge adjustments
Airflow has no relation to superheat or subcooling readings
Charge should always be adjusted first regardless of airflow
Static pressure readings are illegal to use for diagnosis

NEC Reference: NULL

Question 20: A blower motor runs, but airflow is much lower than the unit's rated CFM, and the filter, coil, and ducts all check out clean and correctly sized. What should the technician suspect?

The outdoor condenser fan capacitor
A blower motor or speed tap setting problem
The thermostat display backlight
The refrigerant type in the system

NEC Reference: NULL

Question 21: True or False: A frozen evaporator coil can occur from low refrigerant charge even if airflow is completely normal.

False, icing can only be caused by airflow problems
False, low charge never causes coil icing
True
False, icing only happens with overcharge

NEC Reference: NULL

Question 22: What is a "temperature split" check, and how does it relate to airflow?

It measures voltage drop across the compressor
The difference between return and supply air temperature, useful for spotting airflow or charge issues
It measures refrigerant pressure drop across the metering device only
It has no connection to airflow diagnostics

NEC Reference: NULL

Question 23: A technician finds the evaporator coil fins badly bent and crushed in several areas. How can this affect the system?

Bent fins have no effect on airflow
Bent fins restrict airflow and reduce heat transfer
Bent fins always increase system capacity
Bent fins only affect refrigerant color

NEC Reference: NULL

Question 24: A larger-capacity replacement system is installed on the same old, undersized ductwork. What airflow problem is likely?

Ductwork size never affects a replacement system
The old ducts will automatically resize themselves
Refrigerant charge alone determines airflow, not ductwork
The ducts may restrict airflow, causing high static pressure and reduced airflow

NEC Reference: NULL

Question 25: Besides static pressure, what is another way a technician can estimate system airflow (CFM)?

Checking the color of the refrigerant only
Reading the compressor nameplate voltage only
Using temperature split or a flow hood/anemometer
Airflow cannot be measured or estimated in the field

NEC Reference: NULL

Question 26: True or False: Cleaning a dirty evaporator coil can restore lost cooling capacity and improve superheat readings toward normal.

False, coil cleaning has no effect on capacity
False, a dirty coil actually improves heat transfer
False, only refrigerant charge affects capacity
True

NEC Reference: NULL

Question 27: After thawing a frozen evaporator coil, what is a logical order for the technician to check possible causes?

Replace the compressor first before checking anything else
Check filter and airflow first, then refrigerant charge if airflow is normal
Add refrigerant first without checking anything else
Rewire the thermostat before any other checks

NEC Reference: NULL

Question 28: A homeowner reports the system ices up only after running for several hours, and airflow feels weaker toward the end of a long run. What does this pattern suggest?

The thermostat display is broken
A marginal airflow or charge issue that worsens as ice slowly builds
The outdoor unit is oversized for the home
The system is using the wrong refrigerant type entirely

NEC Reference: NULL

Question 29: A return air grille is partially blocked by furniture. Why should a technician point this out to the homeowner?

Blocking the return restricts airflow the blower can pull in
It has no effect since supply registers matter more
It only affects the thermostat reading
It permanently damages the compressor immediately

NEC Reference: NULL

Question 30: Which statement best summarizes proper airflow diagnostics on an AC system?

Refrigerant charge should always be adjusted before checking airflow
Airflow problems can mimic charge problems, so airflow should be confirmed first
Airflow has no effect on system diagnostics
Only the outdoor unit needs airflow checks

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)