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NATE_AC_SERVICE NEC 2023

NATE AC Service Practice Test 6

This test focuses on condenser-side diagnostics, including dirty condenser coils, failed condenser fan motors, and high head pressure. You will practice connecting outdoor unit problems to overall system performance.

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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: A dirty condenser coil or a failed condenser fan both raise head pressure. High head pressure raises subcooling and puts extra load on the compressor.

30

Questions

30 min

Time

70%

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NATE AC Service Practice Test 6 — Question List

Question 1: What is the main job of the outdoor condenser coil?

To reject heat from the refrigerant to outdoor air, condensing it to liquid
To absorb heat from indoor air only
To store refrigerant during the off cycle
To measure outdoor humidity

Question 2: What happens when the outdoor condenser coil is covered in dirt, grass clippings, or debris?

It has no effect on head pressure
It restricts airflow and raises head pressure
It always lowers subcooling
It reduces compressor workload

Question 3: A condenser fan motor has failed and the fan is not spinning, but the compressor is still running. What happens to head pressure?

Head pressure drops to zero immediately
Head pressure stays completely normal
Head pressure rises quickly due to lost airflow
Head pressure only affects the indoor coil, not this scenario

Question 4: What is the purpose of the high-pressure switch on a residential AC system?

To increase refrigerant charge automatically
To control indoor thermostat setpoint
To slow the blower motor during high humidity
To stop the compressor if discharge pressure rises above a safe limit

Question 5: A technician finds high head pressure and high subcooling, but confirms the refrigerant charge is correct by weight. What should be checked next?

Condenser airflow, such as a dirty coil or failed fan
The indoor thermostat wiring
The evaporator drain line
The indoor blower speed setting only

Question 6: What type of motor is most commonly used for residential condenser fans?

A three-phase induction motor exclusively
PSC (Permanent Split Capacitor) motor
A stepper motor
A DC brushless motor exclusively

Question 7: A condenser fan spins slowly and seems to struggle to reach full speed. The technician tests the run capacitor and finds it well below its rated MFD. What is the likely fix?

Add refrigerant to the system
Increase the thermostat setpoint
Replace the weak run capacitor with a correctly rated one
Remove the fan motor entirely

Question 8: A condensing unit is installed with shrubs growing close on all sides, blocking airflow clearance. What problem can this cause?

It improves system efficiency by shading the unit
It has no effect since only the coil surface matters
It always lowers head pressure
It can cause recirculated warm air and raise head pressure

Question 9: On a cool day with low outdoor temperature, what generally happens to head pressure compared to a hot day, assuming charge and airflow are normal?

Head pressure is generally lower on cooler days
Head pressure always stays exactly the same regardless of outdoor temperature
Head pressure always rises as outdoor temperature drops
Outdoor temperature has no relation to head pressure

Question 10: A technician hears a rattling noise from the outdoor unit and finds the condenser fan blade is loose on its motor shaft. What is the risk if this is not corrected?

There is no risk, loose blades are normal
The blade could shift further, strike the shroud, and cause more damage
It will automatically tighten itself over time
It only affects indoor comfort, not the unit itself

Question 11: If a system runs for a long time with abnormally high head pressure due to a dirty condenser coil, what long-term risk does the compressor face?

There is no long-term risk to the compressor
The compressor will automatically reduce its own workload permanently
The compressor can overheat, wear prematurely, or fail
High head pressure only affects the evaporator, never the compressor

Question 12: What is a common, safe method for cleaning a dirty outdoor condenser coil?

Scrub hard with a wire brush while the unit is running
Spray high-pressure water directly into the electrical compartment
Leave the coil dirty since cleaning voids the warranty
Turn off power, then gently rinse or use an approved coil cleaner

Question 13: A condenser fan runs at what seems like normal speed, but airflow feels weak and head pressure is high. The coil is clean. What should the technician check next?

The fan blade itself, for wrong pitch, damage, or incorrect orientation
The indoor thermostat display
The evaporator drain pan
The liquid line filter drier

Question 14: True or False: On most standard residential systems, the condenser fan and compressor are wired to run together, cycling on and off at the same time.

False, the fan and compressor always run independently
True
False, the fan only runs during heating mode
False, the compressor never needs the fan running

Question 15: A technician finds normal head pressure, low subcooling, and confirms the condenser coil and fan are both in good condition. What does this pattern suggest?

The condenser fan motor bearings are worn
The indoor blower speed is too high
The refrigerant charge is likely low (undercharge)
The system needs no further action since everything is normal

Question 16: Why should a technician avoid using a high-pressure washer directly on condenser coil fins?

High pressure always improves fin performance
There is no risk to the fins from high pressure water
It will automatically straighten any bent fins
High pressure can bend or crush the thin fins, reducing airflow

Question 17: A technician measures the condenser fan motor's amp draw and compares it to the nameplate full-load amps (FLA). Why is this a useful diagnostic step?

High amp draw above nameplate can indicate a failing motor or bad capacitor
Amp draw has no relation to motor condition
Nameplate ratings are only used for compressors, never fan motors
Amp draw only matters for three-phase equipment

Question 18: Outdoor air is 95°F, and the head pressure converts to a 120°F condensing temperature. What is the condenser split (condensing temperature over ambient)?

25°F
215°F
95°F
120°F

Question 19: A system repeatedly trips its high-pressure switch. What should the technician investigate as likely root causes before simply resetting the switch?

Nothing, the switch should simply be reset and ignored
Only the thermostat batteries need to be checked
Dirty coil, failed fan, overcharge, or restricted outdoor airflow
Only the indoor filter needs to be checked

Question 20: A condensing unit is installed in a small, enclosed side yard with a tall fence on three sides and little airflow path to escape. What long-term problem is likely?

The enclosure will always improve system efficiency
There is no possible effect from an enclosed installation
The refrigerant type must be changed to compensate
Reduced heat rejection from trapped air, leading to chronically higher head pressure

Question 21: On a dual run capacitor, the FAN section tests out of tolerance but the HERM (compressor) section tests fine. What does this most likely explain?

The condenser fan may run weak or fail while the compressor still runs normally
The whole unit will be completely dead with no operation at all
The compressor will immediately fail as well
This has no effect on either motor

Question 22: Why do manufacturers specify a minimum clearance distance around an outdoor condensing unit?

It is only a cosmetic recommendation with no technical basis
To ensure proper airflow and prevent recirculation, maintaining normal head pressure
It is required only for indoor units, not outdoor units
It relates only to electrical safety, not airflow

Question 23: After a fan motor replacement, a technician notices the new motor spins in the opposite direction of the old one, pulling air the wrong way through the coil. What is the likely consequence?

There is no consequence, fan direction never matters
The compressor will run more efficiently as a result
Reduced or reversed airflow can cause poor heat rejection and high head pressure
It will automatically correct itself after a few cycles

Question 24: A technician converts head pressure to saturation temperature using a PT chart and compares it to outdoor ambient temperature. Why is this comparison useful?

This comparison has no diagnostic value
It only applies to evaporator coil diagnostics
It measures indoor humidity levels only
It shows how well the condenser rejects heat compared to ambient temperature

Question 25: A three-phase scroll compressor was rewired after a repair. It now runs noisily, draws low amps, and suction and discharge pressures stay nearly equal. What is the likely problem?

A compressor winding is shorted to ground and drawing low current
The compressor is running backward because two supply phases were swapped
The system is overcharged, so the pressures have equalized
Low contactor coil voltage is causing the contacts to chatter

Question 26: A system has both a badly overcharged refrigerant level and a dirty condenser coil at the same time. What can be said about head pressure and subcooling in this case?

The two problems will cancel each other out, giving normal readings
Both problems push subcooling and head pressure higher, worsening the readings
Only the overcharge will show any effect on readings
Only the dirty coil will show any effect on readings

Question 27: What tool does a technician use to check whether a condenser fan run capacitor is within its rated microfarad tolerance?

A combustion analyzer
A manometer
A capacitance meter or multimeter with capacitance function
A refrigerant scale

Question 28: A technician finds a bird nest and debris packed inside the condenser fan grille, partially blocking discharge airflow. What should be done?

Leave the debris in place since it does not affect airflow
Add refrigerant to compensate for the blockage
Increase blower speed indoors to compensate
Safely remove the debris with power off, then confirm normal airflow and pressures

Question 29: True or False: A fin comb tool can be used to carefully straighten bent condenser coil fins and help restore airflow.

True
False, fin combs are only used on evaporator coils
False, bent fins can never be repaired in any way
False, fin combs are used only for cleaning, not straightening

Question 30: An outdoor unit installed under a low deck shows air entering the coil at 108°F while outdoor air is 92°F. What is happening?

The unit is recirculating its own hot discharge air, raising head pressure
The condenser coil is oversized for the compressor it is matched with
The refrigerant charge is low, so the coil is running hot
The condenser fan is turning too fast and heating the air

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)