HVAC and Refrigeration Troubleshooting — real-world interview & field troubleshooting questions with clear, practical answers. Tap any question to open its answer. Showing the first 70 questions free. The complete question bank is available as a PDF below. COMPRESSOR ELECTRICAL & MECHANICAL FAILURES (HERMETIC, SCROLL, SCREW) Q1 An HVAC scroll compressor draws locked rotor amperage (LRA), hums loudly, and trips on internal thermal overload within 3 seconds. Cause? Answer Mechanical seizure (bearing lockup, liquid slugging damage, or debris jamming scroll wraps), a failed dual-run capacitor (open circuit), or an open single-phase winding on 3-phase units. Q2 A semi-hermetic reciprocating compressor repeatedly snaps its suction reed valves. What operating condition is occurring? Answer Liquid refrigerant floodback. Liquid refrigerant returning through the suction line cannot be compressed ($V_{liquid}$ is incompressible); when the piston hits liquid, hydraulic pressure ...