HVAC Technician Interview Questions
& Model Answers, 2026

Type I covers small appliances, Type II high-pressure systems (most residential and commercial split systems and heat pumps), Type III low-pressure systems (centrifugal chillers), and Universal is all three. Say which you hold, and say why it matters: under Section 608 of the Clean Air Act you cannot legally purchase or handle refrigerant without it, and it does not expire. If you only hold Type II, say so and say you are testing for Universal.

Order matters. Confirm the complaint and check the simple things first, thermostat setting and batteries, breaker, filter, and airflow, because a plugged filter or a dirty coil looks like a refrigerant problem to a lazy tech. Then verify airflow across the evaporator, check the contactor and capacitor, and only then put gauges on and take superheat and subcooling to see what the system is actually telling you. State a conclusion, not a guess, and always look for the cause of the failure, not just the failure.

Superheat is the heat added to the refrigerant vapour past the point of complete evaporation; it tells you how well the evaporator is fed. Subcooling is the heat removed below the condensing temperature; it tells you about the charge and the condenser. On a fixed-orifice system you charge by superheat; on a TXV system you charge by subcooling and use superheat to confirm the metering device. High superheat plus low subcooling points to undercharge or a restriction; low superheat plus high subcooling points to overcharge. Say you never add refrigerant without both readings and a leak search.

Core removal tools and large-diameter hoses on both service ports, a good vacuum pump with clean oil, and, above all, a micron gauge, not a clock and not the compound gauge. Pull to 500 microns or better, valve off the pump, and watch for a decay: a rise that levels off means moisture, a rise that keeps climbing means a leak. If you say 'pull a vacuum for twenty minutes,' you have told the interviewer you will produce callbacks.

Two things: what is legal, and what is honest. Venting is illegal, so refrigerant gets recovered, and topping off a leaking system without repairing it is a service you should not sell. Then explain the real choice in plain terms: locate and repair the leak, evacuate and recharge by weight, versus replace, given the age, the refrigerant type and phase-down cost, and the condition of the compressor. Give the price of both and let the customer decide.

That is a flame-sensing or flame-proving failure in most cases. Walk the sequence of operations out loud: call for heat, inducer and pressure switch proving, ignitor, gas valve, flame sense, blower. A dirty flame sensor with weak microamp signal is the classic; also check the flame rectification path, grounding, a cracked or misaligned burner, and the pressure switch reacting to a partially blocked flue. Naming the sequence of operations is the answer that tells them you were trained properly.

Have one ready and do not dodge. Name the actual cause, a leak you did not find because you did not pressure test, a charge you set without checking airflow, an evacuation you cut short, then what you did (went back, on your own time if that is true, made it right) and the practice you changed. The wrong answer is 'I have never had a callback.' Every experienced technician has, and interviewers know it.

Show, do not tell. Take a photo of the burnt contactor or the rusted heat exchanger, show the readings on your gauges or meter, and explain in plain language what happens if it is not fixed. Give the option of repair versus replace with real numbers and no pressure. Say clearly that you do not sell parts a system does not need, that reputation is the whole business in residential service.

Sixty to ninety seconds: your EPA 608 type, years in the trade, whether your depth is residential service, commercial, or refrigeration, one system type you know cold (heat pumps, rooftop units, chillers), and what you are looking for. Lead with the certification and the segment, that is what the service manager is filtering for.

Be honest that peak season is where corners get cut, and say what you do about it: the same diagnostic sequence on every call regardless of the queue, readings recorded rather than remembered, and telling dispatch when a call genuinely needs more time instead of leaving a half-fixed system that comes back tomorrow. A callback in July costs the company more than the extra twenty minutes.

Anchor to data: BLS OEWS May 2025 puts the HVAC median at $61,010/yr ($29.33/hr), with the top 10% above $95,210, and commercial refrigeration sits at the top of that spread. Give an hourly range for your certification level and segment, then ask about the parts that actually decide the cheque: on-call rotation and how it is paid, overtime in peak season, and whether there is commission or spiff on equipment sales.

Many residential companies pay a base plus commission on maintenance agreements and equipment sales. Ask the mechanics: percentage on what, paid when, and clawed back if the customer cancels. Then ask the uncomfortable question, is the technician expected to sell replacements on service calls? A pay plan that rewards selling a system rather than fixing one tells you what kind of shop it is.

Price them out: a take-home truck with fuel is worth real money, as is a company-supplied tool allowance, paid EPA and NATE testing, and paid manufacturer training. On-call is the other side of the ledger, ask how many weeks in the rotation, what the callout minimum pays, and whether peak-season overtime is expected or optional. Two offers at the same hourly rate are often thousands apart once you add it up.