MOBILE A/C SERVICE TECHNICIAN CERTIFICATION EXAM
PRACTICE QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES Q&A INSTANT DOWNLOAD PDF
140 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze complex A/C system failures using advanced diagnostic reasoning
2 Evaluate refrigerant properties and apply proper handling techniques per EPA regulations
3 Integrate knowledge of electrical systems, thermodynamics, and mechanical components to optimize
system performance
4 Apply safety and environmental standards in all service procedures
5 Mobile A
6 C Service Technician Certification Exam Practice Questions And Correct Answers
7 Verified Answers
8 Plus Rationales Q&A Instant Download Pdf
9 Foundations of Mobile Air Conditioning Systems and Service
10 Applied Mobile Air Conditioning Systems and Service
11 Advanced Mobile Air Conditioning Systems and Service
12 Mobile Air Conditioning Systems and Service Review
Page 1
,Q1 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
During a performance test, an R-134a system with a fixed orifice tube exhibits low
evaporator outlet pressure and high superheat at the evaporator outlet. The
compressor is cycling on low-pressure cutoff. Which of the following is the most
likely root cause?
A. A restricted orifice tube causing starvation of the evaporator CORRECT
B. An overcharged system causing liquid slugging
C. A faulty evaporator temperature sensor
D. A weak compressor reed valve causing low volumetric efficiency
RATIONALE: Low evaporator pressure with high superheat indicates insufficient refrigerant flow
through the evaporator, typical of a restricted orifice tube. Overcharge would cause high
pressures and low superheat. A weak compressor would cause high superheat but not
necessarily low evaporator pressure (would be high). A faulty sensor wouldn't affect actual
pressures.
Q2 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
A technician recovers refrigerant from an R-1234yf system using a recovery
machine certified for R-134a. What is the primary safety and regulatory violation?
A. R-1234yf is mildly flammable, and the recovery machine is not rated for flammable
refrigerants. CORRECT
B. R-1234yf has a higher global warming potential than R-134a, requiring special handling.
C. The recovery machine's hoses are not compatible with R-1234yf's chemical composition.
D. R-1234yf requires a different refrigerant oil, and cross-contamination will damage the system.
RATIONALE: R-1234yf is classified as mildly flammable (A2L), and recovery equipment must be
specifically approved for flammable refrigerants to prevent ignition risks. EPA regulations
mandate using certified equipment for each refrigerant type. While hoses may be compatible, the
flammability is the critical issue. GWP of R-1234yf is lower than R-134a, not higher. Oil
compatibility is not the primary violation.
Page 2
,Q3 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
In a variable displacement compressor system, the control valve is stuck in the
maximum displacement position. Which of the following parameter changes is
most likely observed during a performance test?
A. High evaporator pressure and low compressor suction pressure
B. High discharge pressure and low evaporator pressure CORRECT
C. Low discharge pressure and high evaporator pressure
D. Normal discharge pressure but excessively low suction pressure
RATIONALE: A stuck maximum displacement valve causes the compressor to run at full stroke,
increasing refrigerant flow and compression work. This leads to high discharge pressure and,
because the evaporator cannot handle the increased flow, the evaporator pressure drops. This is
a classic symptom. Other options misrepresent the pressure dynamics.
Q4 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
Per SAE J2788, when recovering refrigerant from a system with a known leak,
what is the required final vacuum level to ensure proper recovery?
A. 0 psig (atmospheric pressure)
B. 15 inches Hg vacuum
C. 20 inches Hg vacuum
D. 25 inches Hg vacuum CORRECT
RATIONALE: SAE J2788 specifies that recovery equipment must be capable of pulling a vacuum
of at least 25 inches Hg to ensure that the majority of refrigerant is removed, especially in
systems with leaks. This prevents venting and ensures compliance with EPA regulations. Lower
vacuums are insufficient for thorough recovery.
Page 3
, Q5 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
A technician is retrofitting an R-12 system to R-134a. After replacing the desiccant,
which of the following procedures is critical to prevent cross-contamination and
ensure system compatibility?
A. Flushing the system with mineral oil to remove old refrigerant
B. Installing a new expansion valve calibrated for R-134a
C. Evacuating the system to 500 microns before charging
D. Adding a retrofit label indicating the new refrigerant type CORRECT
RATIONALE: A retrofit label is mandatory per EPA regulations to inform future service personnel
of the refrigerant change, preventing accidental recharge with the wrong refrigerant. Flushing
with mineral oil is not recommended; the system should be flushed with appropriate solvent. The
expansion valve may need adjustment but not necessarily replacement. Evacuation is important
but not specific to retrofitting.
Q6 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
In an R-134a system, the high-side pressure is 250 psig and the low-side pressure
is 30 psig. The ambient temperature is 90°F. The technician measures the
temperature of the liquid line at the condenser outlet as 130°F. What is the
condenser subcooling?
A. 10°F
B. 20°F CORRECT
C. 30°F
D. 40°F
RATIONALE: Subcooling is the difference between the condensing temperature (saturation
temperature corresponding to high-side pressure) and the actual liquid line temperature. For
R-134a at 250 psig, the saturation temperature is approximately 150°F. The liquid line
temperature is 130°F, so subcooling = 150 - 130 = 20°F. Other options are miscalculations.
Page 4
PRACTICE QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES Q&A INSTANT DOWNLOAD PDF
140 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze complex A/C system failures using advanced diagnostic reasoning
2 Evaluate refrigerant properties and apply proper handling techniques per EPA regulations
3 Integrate knowledge of electrical systems, thermodynamics, and mechanical components to optimize
system performance
4 Apply safety and environmental standards in all service procedures
5 Mobile A
6 C Service Technician Certification Exam Practice Questions And Correct Answers
7 Verified Answers
8 Plus Rationales Q&A Instant Download Pdf
9 Foundations of Mobile Air Conditioning Systems and Service
10 Applied Mobile Air Conditioning Systems and Service
11 Advanced Mobile Air Conditioning Systems and Service
12 Mobile Air Conditioning Systems and Service Review
Page 1
,Q1 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
During a performance test, an R-134a system with a fixed orifice tube exhibits low
evaporator outlet pressure and high superheat at the evaporator outlet. The
compressor is cycling on low-pressure cutoff. Which of the following is the most
likely root cause?
A. A restricted orifice tube causing starvation of the evaporator CORRECT
B. An overcharged system causing liquid slugging
C. A faulty evaporator temperature sensor
D. A weak compressor reed valve causing low volumetric efficiency
RATIONALE: Low evaporator pressure with high superheat indicates insufficient refrigerant flow
through the evaporator, typical of a restricted orifice tube. Overcharge would cause high
pressures and low superheat. A weak compressor would cause high superheat but not
necessarily low evaporator pressure (would be high). A faulty sensor wouldn't affect actual
pressures.
Q2 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
A technician recovers refrigerant from an R-1234yf system using a recovery
machine certified for R-134a. What is the primary safety and regulatory violation?
A. R-1234yf is mildly flammable, and the recovery machine is not rated for flammable
refrigerants. CORRECT
B. R-1234yf has a higher global warming potential than R-134a, requiring special handling.
C. The recovery machine's hoses are not compatible with R-1234yf's chemical composition.
D. R-1234yf requires a different refrigerant oil, and cross-contamination will damage the system.
RATIONALE: R-1234yf is classified as mildly flammable (A2L), and recovery equipment must be
specifically approved for flammable refrigerants to prevent ignition risks. EPA regulations
mandate using certified equipment for each refrigerant type. While hoses may be compatible, the
flammability is the critical issue. GWP of R-1234yf is lower than R-134a, not higher. Oil
compatibility is not the primary violation.
Page 2
,Q3 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
In a variable displacement compressor system, the control valve is stuck in the
maximum displacement position. Which of the following parameter changes is
most likely observed during a performance test?
A. High evaporator pressure and low compressor suction pressure
B. High discharge pressure and low evaporator pressure CORRECT
C. Low discharge pressure and high evaporator pressure
D. Normal discharge pressure but excessively low suction pressure
RATIONALE: A stuck maximum displacement valve causes the compressor to run at full stroke,
increasing refrigerant flow and compression work. This leads to high discharge pressure and,
because the evaporator cannot handle the increased flow, the evaporator pressure drops. This is
a classic symptom. Other options misrepresent the pressure dynamics.
Q4 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
Per SAE J2788, when recovering refrigerant from a system with a known leak,
what is the required final vacuum level to ensure proper recovery?
A. 0 psig (atmospheric pressure)
B. 15 inches Hg vacuum
C. 20 inches Hg vacuum
D. 25 inches Hg vacuum CORRECT
RATIONALE: SAE J2788 specifies that recovery equipment must be capable of pulling a vacuum
of at least 25 inches Hg to ensure that the majority of refrigerant is removed, especially in
systems with leaks. This prevents venting and ensures compliance with EPA regulations. Lower
vacuums are insufficient for thorough recovery.
Page 3
, Q5 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
A technician is retrofitting an R-12 system to R-134a. After replacing the desiccant,
which of the following procedures is critical to prevent cross-contamination and
ensure system compatibility?
A. Flushing the system with mineral oil to remove old refrigerant
B. Installing a new expansion valve calibrated for R-134a
C. Evacuating the system to 500 microns before charging
D. Adding a retrofit label indicating the new refrigerant type CORRECT
RATIONALE: A retrofit label is mandatory per EPA regulations to inform future service personnel
of the refrigerant change, preventing accidental recharge with the wrong refrigerant. Flushing
with mineral oil is not recommended; the system should be flushed with appropriate solvent. The
expansion valve may need adjustment but not necessarily replacement. Evacuation is important
but not specific to retrofitting.
Q6 ANALYZE COMPLEX A/C SYSTEM FAILURES USING ADVANCED DIAGNOSTIC
REASONING
In an R-134a system, the high-side pressure is 250 psig and the low-side pressure
is 30 psig. The ambient temperature is 90°F. The technician measures the
temperature of the liquid line at the condenser outlet as 130°F. What is the
condenser subcooling?
A. 10°F
B. 20°F CORRECT
C. 30°F
D. 40°F
RATIONALE: Subcooling is the difference between the condensing temperature (saturation
temperature corresponding to high-side pressure) and the actual liquid line temperature. For
R-134a at 250 psig, the saturation temperature is approximately 150°F. The liquid line
temperature is 130°F, so subcooling = 150 - 130 = 20°F. Other options are miscalculations.
Page 4
