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Michigan (MI) Unlimited Refrigeration & Air
Conditioning Service Exam COMPLETE QUESTIONS
AND DETAILED SOLUTIONS LATEST UPDATE THIS
YEAR-JUST RELEASED
SUMMARIZED EXAM COVERAGE
• Refrigeration cycle and thermodynamics
• Refrigerant handling, recovery, and EPA compliance
• Compressor, evaporator, condenser operation and faults
• TXV and refrigerant flow control devices
• Electrical controls and motor protection systems
• System diagnostics using pressures and temperatures
• Installation, charging, evacuation, and commissioning
• Safety standards and regulatory compliance
• Preventive maintenance and efficiency optimization
Q1
A refrigeration system is running but the evaporator coil shows heavy frost buildup and reduced cooling
performance; what is the most likely cause?
A. Excessively high condenser temperature
B. Restricted airflow across evaporator due to dirty filter or fan failure
C. Overcharged refrigerant system
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D. High ambient humidity only
Answer: B
Rationale: Poor airflow causes coil freezing and reduced heat exchange.
Q2
A technician measures low suction pressure and high superheat in a refrigeration system; what is the
most likely problem?
A. Overcharged system
B. Undercharged refrigerant or refrigerant restriction
C. Dirty condenser coil
D. Oversized compressor
Answer: B
Rationale: Low suction and high superheat indicate low refrigerant flow.
Q3
A compressor in an air conditioning system is overheating and tripping on thermal overload; what is the
most likely cause?
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A. Proper refrigerant charge
B. Insufficient refrigerant return causing inadequate motor cooling
C. Oversized evaporator coil
D. Excess airflow
Answer: B
Rationale: Compressors rely on refrigerant for cooling.
Q4
A refrigeration system shows high head pressure and poor cooling performance during hot weather;
what is the most likely cause?
A. Low indoor load
B. Dirty condenser coil or inadequate condenser airflow
C. Low refrigerant charge
D. Oversized evaporator
Answer: B
Rationale: Heat rejection problems raise head pressure.
Q5
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A technician finds bubbles in the sight glass of a refrigeration system; what is the most likely
explanation?
A. Overcharged system
B. Low refrigerant charge or flashing due to pressure drop
C. Excess condenser airflow
D. High subcooling
Answer: B
Rationale: Bubbles indicate insufficient liquid refrigerant.
Q6
A split air conditioning system has frozen suction line and reduced airflow; what is the most likely cause?
A. High refrigerant subcooling
B. Restricted airflow due to dirty filter or evaporator coil
C. Excessive condenser fan speed
D. Oversized compressor
Answer: B
Rationale: Airflow restriction causes coil freezing.
Michigan (MI) Unlimited Refrigeration & Air
Conditioning Service Exam COMPLETE QUESTIONS
AND DETAILED SOLUTIONS LATEST UPDATE THIS
YEAR-JUST RELEASED
SUMMARIZED EXAM COVERAGE
• Refrigeration cycle and thermodynamics
• Refrigerant handling, recovery, and EPA compliance
• Compressor, evaporator, condenser operation and faults
• TXV and refrigerant flow control devices
• Electrical controls and motor protection systems
• System diagnostics using pressures and temperatures
• Installation, charging, evacuation, and commissioning
• Safety standards and regulatory compliance
• Preventive maintenance and efficiency optimization
Q1
A refrigeration system is running but the evaporator coil shows heavy frost buildup and reduced cooling
performance; what is the most likely cause?
A. Excessively high condenser temperature
B. Restricted airflow across evaporator due to dirty filter or fan failure
C. Overcharged refrigerant system
, Page 2 of 112
D. High ambient humidity only
Answer: B
Rationale: Poor airflow causes coil freezing and reduced heat exchange.
Q2
A technician measures low suction pressure and high superheat in a refrigeration system; what is the
most likely problem?
A. Overcharged system
B. Undercharged refrigerant or refrigerant restriction
C. Dirty condenser coil
D. Oversized compressor
Answer: B
Rationale: Low suction and high superheat indicate low refrigerant flow.
Q3
A compressor in an air conditioning system is overheating and tripping on thermal overload; what is the
most likely cause?
, Page 3 of 112
A. Proper refrigerant charge
B. Insufficient refrigerant return causing inadequate motor cooling
C. Oversized evaporator coil
D. Excess airflow
Answer: B
Rationale: Compressors rely on refrigerant for cooling.
Q4
A refrigeration system shows high head pressure and poor cooling performance during hot weather;
what is the most likely cause?
A. Low indoor load
B. Dirty condenser coil or inadequate condenser airflow
C. Low refrigerant charge
D. Oversized evaporator
Answer: B
Rationale: Heat rejection problems raise head pressure.
Q5
, Page 4 of 112
A technician finds bubbles in the sight glass of a refrigeration system; what is the most likely
explanation?
A. Overcharged system
B. Low refrigerant charge or flashing due to pressure drop
C. Excess condenser airflow
D. High subcooling
Answer: B
Rationale: Bubbles indicate insufficient liquid refrigerant.
Q6
A split air conditioning system has frozen suction line and reduced airflow; what is the most likely cause?
A. High refrigerant subcooling
B. Restricted airflow due to dirty filter or evaporator coil
C. Excessive condenser fan speed
D. Oversized compressor
Answer: B
Rationale: Airflow restriction causes coil freezing.
