313D Troubleshooting and System Diagnosis 3

Question 1

A technician measures a compressor drawing high amperage with low suction and high discharge pressure. What is the most likely diagnosis?

Accepted Answer

Refrigerant overcharge

Answer

Refrigerant overcharge increases system pressures and compressor workload, resulting in elevated amperage draw.

Question 2

A homeowner complains of short cycling. The technician measures that the compressor runs for less than 2 minutes per cycle. Which component should be tested first?

Accepted Answer

High and low pressure safety switches

Answer

Short cycling is frequently caused by pressure switches that trip due to abnormal operating pressures, making them the first item to test.

Question 3

A technician notices the system cools adequately in the morning but loses capacity significantly in the afternoon heat. Which diagnosis is most consistent with this behavior?

Accepted Answer

Dirty or blocked condenser coil

Answer

A partially blocked condenser coil can handle lighter loads in cooler morning temperatures but cannot reject adequate heat when ambient temperatures peak in the afternoon.

Question 4

While troubleshooting a residential system, a technician finds oil stains near the compressor service valves. What does this indicate?

Accepted Answer

A refrigerant and oil leak at that location

Answer

Oil stains near refrigerant connections indicate a refrigerant leak, since oil travels with refrigerant and deposits at leak points.

Question 5

What is the purpose of measuring the temperature difference across a filter-drier (liquid line drier) during operation?

Accepted Answer

To detect a restriction inside the drier

Answer

A notable temperature drop across a filter-drier (more than 1–2°F) indicates the drier is restricted and should be replaced.

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test

313D Troubleshooting and System Diagnosis 3