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NATE_AC_SERVICE NEC 2023

NATE AC Service Practice Test 7

This test covers refrigerant leak detection methods, recovery procedures, and system evacuation with a vacuum pump. You will practice choosing the right method for each situation.

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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: Recover refrigerant before opening a sealed system, and always evacuate with a vacuum pump to remove air and moisture before charging.

30

Questions

30 min

Time

70%

Pass

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NATE AC Service Practice Test 7 — Question List

Question 1: What is an electronic leak detector used for?

To sense refrigerant gas in the air near a possible leak
To measure duct static pressure
To measure compressor amp draw
To test capacitor microfarad rating

Question 2: How does the UV dye leak detection method work?

It measures the leak rate by changing the system pressure
It measures the exact leak rate in ounces per year
A dye circulates in the system and glows under UV light at leak points
It only works on the high side of the system

Question 3: How does the soap bubble leak detection method work?

It measures refrigerant temperature at the joint
It requires the system to be fully evacuated first
It only works with R-22 refrigerant
Bubbles form at the leak point when gas escapes through the solution

Question 4: What is a nitrogen pressure test used for in leak detection?

Pressurizing with nitrogen and watching for a pressure drop over time
Injecting oil to seal small leaks permanently
Measuring the leak rate in ounces per year
Testing only the electrical control circuit

Question 5: Why must a technician recover refrigerant before opening a sealed system for repair, such as replacing a compressor?

Because it makes the repair take longer on purpose
Because venting refrigerant to the atmosphere is illegal and harmful to the environment
Because recovered refrigerant is always thrown away
Because it increases refrigerant cost with no other benefit

Question 6: What is the purpose of evacuating a refrigerant system with a vacuum pump before charging?

To increase the refrigerant charge automatically
To test the compressor amp draw
To remove air and moisture from the system before charging
To warm the refrigerant before charging

Question 7: What does a micron gauge measure during system evacuation?

Compressor amp draw
Indoor humidity percentage
Outdoor ambient temperature
The depth of vacuum in the system, more precisely than a standard gauge

Question 8: True or False: Pulling a deep vacuum helps boil off and remove trace moisture from inside the refrigerant system.

True
False, moisture cannot be removed by vacuum, only by heat
False, evacuation only affects air, never moisture
False, deep vacuum has no relation to moisture removal

Question 9: A technician pulls a vacuum on a system, but the micron reading quickly rises back up after the pump is shut off and valved off. What does this suggest?

The system is functioning normally with no concerns
The vacuum pump oil needs to be changed only
The system likely has a leak letting air back in
The refrigerant charge was added too quickly

Question 10: Why might a technician use more than one leak detection method, such as an electronic detector and soap bubbles, on the same suspect joint?

It is required by law to use at least two methods every time
Using multiple methods helps confirm the exact leak location and avoid false readings
Electronic detectors never work and must always be paired with soap
It has no benefit and simply wastes time

Question 11: After evacuating a residential R-410A system, which result shows the system is dry and tight?

The compound gauge reads 0 psig
The manifold gauge reaches 29 inches of mercury once
It reaches about 500 microns or lower and holds near that level when isolated from the pump
After isolation, the micron reading climbs steadily back toward atmospheric

Question 12: What equipment does a technician need to properly recover refrigerant from a system before repair?

A recovery machine and an approved recovery cylinder
A combustion analyzer and a megohmmeter
A manometer and a flow hood
A capacitance meter and an ammeter

Question 13: Why can evacuation time vary significantly between different jobs?

Evacuation time is always exactly the same regardless of conditions
System size, moisture, temperature, and leaks can all affect evacuation time
Only the length of the vacuum hoses affects the time
Evacuation time depends only on the technician's experience level, not conditions

Question 14: Why should vacuum pump oil be changed regularly and kept clean?

Pump oil condition has no effect on vacuum performance
It is purely a cosmetic maintenance step
Contaminated oil reduces the pump's ability to reach a deep vacuum
Oil changes are only needed once, at the time of purchase

Question 15: A technician finds a small, steady leak at a Schrader valve core using soap bubbles. What is a likely, simple repair?

Replace the entire outdoor unit
Ignore it since Schrader valves cannot leak
Add more refrigerant to compensate for the loss
Replace the worn or damaged Schrader valve core

Question 16: What is a "triple evacuation" method sometimes used on badly contaminated systems?

Pulling vacuum and breaking it with nitrogen multiple times to flush contaminants
Charging the system three separate times with refrigerant
Testing the compressor three times before starting
Running the condenser fan three times faster than normal

Question 17: Why is it good practice to evacuate a system through both the high-side and low-side service ports at the same time when possible?

It is required only for R-22 systems
It helps remove air and moisture faster and more completely
It has no effect on evacuation speed or completeness
It is only done to check for leaks, not to evacuate

Question 18: True or False: Standard best practice is to find and repair a refrigerant leak, then evacuate the system, before adding a full refrigerant charge.

False, charging should always happen before any leak repair
False, evacuation is never necessary after a repair
True
False, leaks do not need to be repaired if the system still runs

Question 19: After reaching a deep vacuum, a technician isolates the system from the pump and watches the micron gauge for several minutes. What is this step called, and why is it done?

A refrigerant charging test, done to measure total charge weight
A compressor amperage test, done to check motor windings
A static pressure test, done to check duct sizing
A vacuum hold test, done to confirm the system does not have a leak

Question 20: A vacuum pump cannot pull the system below a fairly high micron reading, even after running for a long time. What are two possible explanations?

A leak in the system, or a weak/contaminated vacuum pump
The thermostat batteries are low
The refrigerant type was recently changed
The condenser fan capacitor is weak

Question 21: True or False: Refrigerant recovery is expected even when only a small amount of refrigerant remains in a system before it is opened for repair.

False, small amounts can always be vented freely
True
False, recovery is only required for large commercial systems
False, recovery is optional based on technician preference

Question 22: Why is it worth spending extra time to precisely locate a leak before starting the repair, rather than repairing the first suspect area found?

It has no real benefit and wastes the customer's money
It is required only for warranty claims, never for standard repairs
A precise location avoids unnecessary repairs and reduces the chance of missing the real leak
It is only useful for finding leaks on new installations

Question 23: A technician shines a UV light on a system that had dye added during a previous service call and sees a glowing residue at a fitting. What should the technician do before assuming this is a new, active leak?

Immediately replace the entire line set without further checks
Assume no leak exists since dye was used before
Add refrigerant without any further investigation
Confirm the leak is still active using another detection method

Question 24: Why must a technician recover refrigerant only into a cylinder labeled for that specific refrigerant type?

Mixing refrigerant types contaminates the refrigerant and can be unsafe
It is only a cosmetic labeling requirement with no safety impact
All refrigerants can be safely mixed in any cylinder
Cylinder labeling only matters for new refrigerant, not recovered refrigerant

Question 25: True or False: On a new installation, it makes sense to pressure test the line set and system with nitrogen for leaks before pulling a vacuum and charging.

False, evacuation should always happen before any leak testing
True
False, new installations never need leak testing
False, nitrogen cannot be used on new line sets

Question 26: Why might a technician use liquid recovery instead of vapor-only recovery when a system has a large refrigerant charge?

Liquid recovery is illegal and should never be used
Vapor recovery is always faster for any size of charge
Liquid recovery is generally faster for removing a large charge
There is no difference in speed between the two methods

Question 27: A system sat open to the atmosphere for several days during a compressor replacement. What extra consideration should the technician give to evacuation afterward?

No extra consideration is needed regardless of how long it was open
The refrigerant type should automatically be changed
The compressor warranty is automatically voided by open time
More moisture likely entered, so a longer or repeated evacuation may be needed

Question 28: Which recovery method removes a large liquid charge fastest by using the recovery machine to push vapor back into the system while liquid is pulled out?

Vapor-only recovery from the suction port
Push-pull recovery
System-dependent (passive) recovery
Nitrogen purging

Question 29: Why is it good practice to document the final micron reading achieved during evacuation on the service ticket?

Documentation has no practical value and can be skipped
It provides a record that proper evacuation procedure was followed
It is only required for commercial refrigeration jobs
Micron readings are illegal to record on paperwork

Question 30: Why should an R-410A system not be left open to the atmosphere any longer than necessary during a repair?

R-410A reacts with oxygen in the air and breaks down into R-22
The copper tubing can collapse once internal pressure is lost
Air entering the system freezes solid inside the metering device
Its POE oil quickly absorbs moisture, which forms acids and is hard to evacuate

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)