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HVAC Practice Questions for New Technicians, Worked Through
Early-career HVAC tests and first-year field questions come down to the same thing: can you read what the system is telling you and act in the right order. Numbers matter less than the reasoning that connects them.
Six questions below, each with the answer and the diagnostic logic a good tech would use.
Pick an option to lock it in and see the reasoning straight away. Nothing is timed and nothing is recorded, so answer the way you would on the day rather than the way that looks good.
Question 1
Which component drops high-pressure liquid refrigerant into a low-pressure mixture just before the evaporator?
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C. The metering device
The metering device, whether a fixed orifice or a thermostatic expansion valve, creates the pressure drop that lets refrigerant boil at a low temperature in the evaporator. The compressor raises pressure, the condenser rejects heat and turns vapor to liquid, and the accumulator protects the compressor from liquid floodback. Being able to walk the cycle in order is the foundation every diagnosis sits on.
Question 2
A cooling system shows high superheat and low subcooling. What does this pattern most likely indicate?
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B. Undercharge
High superheat says the evaporator is running out of liquid refrigerant before the coil ends, and low subcooling says there is not enough liquid stacking in the condenser either. Together they point to not enough refrigerant in the system. Look for the leak rather than just adding refrigerant, because a system that was correctly charged and is now low did not lose it by evaporation.
Question 3
A single-phase condenser fan motor hums but will not start turning, and spins freely by hand. What do you check first?
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A. The run capacitor
A motor that hums and will not start has power but no starting torque, and on a PSC motor that torque comes from the capacitor. Check it for capacitance against its rating with the power off and the capacitor discharged. Charge and thermostat wiring do not explain a motor that is energized, and a motor that turns freely by hand argues against a seized bearing.
Question 4
A system's measured total external static pressure is well above the manufacturer's rating. What does this tell you?
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B. There is a restriction in the duct system or filter
High total external static means the blower is fighting the duct system, usually from a dirty filter, an undersized or crushed return, or closed dampers. Low airflow then shows up as low suction pressure, a coil that ices, and a comfort complaint that looks like a refrigerant problem. Measure static before you touch a gauge set, or you will be chasing charge on an airflow fault.
Question 5
A gas furnace lights, runs for a few seconds, then shuts down and repeats the sequence. What is the most likely cause?
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B. A dirty or failed flame sensor
Ignition followed by lockout a few seconds later is the classic flame rectification failure: the board lights the burner, fails to sense a flame through the sensor, and shuts the gas off for safety. Clean the sensor with a light abrasive and check its ground. A failed gas valve would not light at all, and the timing is far too specific for a thermostat fault.
Question 6
Before working inside an energized air handler's control compartment, what is the correct first step?
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B. Kill power at the disconnect, verify it is dead, and lock it out
De-energize at the disconnect, verify absence of voltage with your meter, then lock and tag it. Setting the thermostat to off leaves line voltage present, and pulling a low voltage fuse does nothing about the 240 volt side. Verifying with a meter matters as much as the switching, because a disconnect that looks open is not proof.
Six questions is a sample, not a study plan
Any fixed list of questions has the same problem: work it twice and you are remembering the list rather than learning the material. Techunique generates every scenario fresh against the Entry-level HVAC certification and first-year field readiness (NATE Ready-to-Work level) blueprint, ladders the difficulty to how you are answering, and explains each miss the moment you make it. One full session is free every day.
General HVAC practice. Techunique is not affiliated with NATE or any certification body.
How to get value out of practice questions
- Learn to walk the refrigeration cycle out loud, in order, with pressures and temperatures at each point. Every charging question resolves back to it.
- Measure airflow before you measure charge. Most 'charge problems' on a service call are airflow problems.
- Practice reading schematics rather than memorizing wire colors. Colors vary by manufacturer; the ladder logic does not.
- Get comfortable with your meter on real equipment. Field readings teach faster than any question bank.
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