HVAC technician interview questions

What this hire must get done

Write the scorecard before you interview, then hire against it. Set the bracketed targets from your own numbers.

What to tell candidates before the interview

Say the hard parts plainly. People who wouldn't stay drop out early, and the ones who stay knew what they signed up for.

• Show a typical week in peak season and in the slow season: the hours, on-call and weekend rotation, and how pay works (hourly, flat rate or spiffs).
• Explain that the job includes attics, crawl spaces and rooftops in heat and cold, so candidates can picture the real work.
• Name the checks that come with the job, like a driving record for the company van or a background check, and when they happen. Many states and cities limit when you can ask about criminal records, some until after a job offer.
• Tell them how you expect repair and replacement options to be presented, and that you don't want pressure sales.

How to run the interview

1. Same questions, same order. Ask every candidate the questions below and the same follow-ups. It is the only way to compare people fairly.
2. Two interviewers. An owner or manager and someone who does the work. Take notes on what the candidate says, not on how you feel about them.
3. Score right after each answer. 5 sounds like the strong answer, 3 like the mixed one, 1 like the weak one. Use 2 and 4 for answers in between.
4. Rate alone, then compare. Compare candidates question by question, and talk only after everyone has scored. Big gaps are worth a conversation.

1. Technical · Diagnosis

   A gas furnace won't heat. The inducer runs, but the burners never light. Walk me through how you diagnose it.

   It shows whether they work through the sequence of operation with a meter or guess at the expensive part.

   Follow-ups

   • What does the board's fault code tell you, and what don't you trust it for?
   • What reading would make you stop and replace the pressure switch?
   • What do you check before you leave so you know it's fixed?

   5Strong

   Follows the sequence of operation: reads the fault code, checks the pressure switch, its hose, the venting and condensate drain, the limit and rollout switches, then the igniter, gas supply and valve, proving each with a meter or manometer before replacing anything. Runs a full cycle at the end.

   3Mixed

   Checks the right parts but in a jumbled order, or names the likely fault without saying how they'd prove it.

   1Weak

   Goes straight to the control board or igniter, or skips the venting and safety checks.

2. Behavioral · Diagnosis

   Tell me about the hardest intermittent problem you've tracked down on a system. How did you finally prove what it was?

   Intermittent faults separate technicians who reason from evidence from those who wait for the next callback.

   Follow-ups

   • What did you try first that didn't work?
   • How did you catch the fault when it wasn't happening?
   • What did you tell the customer while you were still looking?

   5Strong

   Describes a specific system, how they caught the fault (a data logger, watching a full cycle, the board's fault history), ruled out causes one at a time, and confirmed the fix over time.

   3Mixed

   Has a real example and found it, but by luck or a hunch they can't fully explain.

   1Weak

   Can't name a specific case, or replaced parts until it stopped.

3. Technical · Refrigerant work

   Walk me through how you check the refrigerant charge on a split AC system with a TXV.

   Charging by feel or by suction pressure alone leads to repeat calls and shorter compressor life.

   Follow-ups

   • What do you check before you connect gauges?
   • Which reading do you trust most here, and why?
   • When would you recover the charge and weigh it back in?

   5Strong

   Checks airflow, the filter and coils first, lets the system run until readings settle, measures subcooling against the manufacturer's chart, and checks superheat to confirm the TXV is working. After a repair that empties the system, weighs in the full charge with the line-set adjustment.

   3Mixed

   Knows subcooling is the method for a TXV but skips the airflow checks or can't say where the target comes from.

   1Weak

   Charges by suction pressure alone, or until the line feels cold.

4. Behavioral · Refrigerant work

   Think of the last time you replaced a part on the refrigerant circuit, like a compressor or coil. Walk me through exactly what you did, from recovery to startup.

   Asking for the last real job, step by step, gets past what they know to what they actually do.

   Follow-ups

   • How did you know the vacuum was good?
   • What did you put in the notes for that job?
   • What would you have done if the system wouldn't hold vacuum?

   5Strong

   Recovered into equipment and cylinders rated for that refrigerant, flowed nitrogen while brazing, replaced the drier, pressure tested with dry nitrogen, pulled down to the manufacturer's micron target and watched it hold with the pump valved off, charged by weight, then checked by the manufacturer's method, and wrote it up.

   3Mixed

   Gets most steps right but ran the pump by the clock or skipped the hold test, and knows the micron gauge should decide.

   1Weak

   Skipped nitrogen, the pressure test or the micron gauge, and sees no problem with that.

5. Technical · Safety judgment

   Newer systems use A2L refrigerants like R-454B and R-32. Walk me through what you do differently when you service one.

   A2L refrigerants are mildly flammable. A technician who hasn't kept up can bring a spark or a torch to a leak.

   Follow-ups

   • What about your tools and recovery cylinders has to change?
   • What do you do before you put a torch on the lines?
   • What would make you stop and call your supervisor?

   5Strong

   Uses a recovery machine, vacuum pump and leak detector rated for A2Ls, and cylinders marked for them. Keeps sparks and flames away, ventilates, recovers and purges with nitrogen before brazing, checks the unit's leak sensor if it has one, and names where they trained on A2Ls.

   3Mixed

   Knows A2Ls are mildly flammable and to follow the manufacturer, but is vague on tools, cylinders or the nitrogen purge before brazing.

   1Weak

   Treats them like any other refrigerant, or hasn't heard of A2Ls.

6. Situational · Safety judgment

   On a tune-up you find high carbon monoxide in the flue and signs of a cracked heat exchanger. The homeowner says they can't afford to deal with it now. What do you do?

   This is the call where a technician's judgment protects a family, and your company's name.

   Follow-ups

   • What would you say to the homeowner, word for word?
   • How would you confirm the crack, and rule out a burner or gas pressure problem?
   • What do you write down, and who at the office do you tell?

   5Strong

   Checks the living space for carbon monoxide and gets people out if needed. Explains the danger plainly, shuts off and red-tags the furnace as company policy, local code and the utility allow, records readings and photos, and offers options. If refused, gets a signed refusal and tells the office.

   3Mixed

   Explains the danger and documents it, but is unsure of the red-tag steps or what to do when the homeowner refuses.

   1Weak

   Leaves it running without a clear warning, or without writing it up and telling the office.

7. Situational · Customer trust

   A homeowner's fifteen-year-old AC has a failed compressor, and they ask what you'd do. What do you tell them?

   How they present options decides whether customers trust your company and stay happy with what they chose.

   Follow-ups

   • What would change your advice?
   • How do you answer if they ask what you'd do in your own house?
   • What do you do if they want time to think?

   5Strong

   Lays out repair and replacement with honest prices, warranty and expected life, answers questions in plain words, gives a straight opinion when asked, and lets them decide without pressure.

   3Mixed

   Gives fair options but leaves out a fact the homeowner needs, like warranty or how long the old system may last, or explains it in terms they can't follow.

   1Weak

   Pushes replacement no matter what, or won't give an opinion when asked.

8. Behavioral · Customer trust

   Tell me about a time a customer was upset before you got in the door, say because you were late or it was a second visit for the same problem. What did you do?

   Late arrivals and second visits happen. The first few minutes at the door often decide whether that customer calls you again.

   Follow-ups

   • What was the customer upset about?
   • What did you say first?
   • How did the visit end, and how did you know?

   5Strong

   Listened first, owned the problem without blaming the office, explained what they'd do and how long it would take, and followed through. Can say how the customer showed they were satisfied at the end.

   3Mixed

   Calmed the customer down but mostly by apologizing, without a clear plan.

   1Weak

   Blamed dispatch or the customer, or says it doesn't happen to them.

9. Behavioral · Owning the work

   Tell me about a callback on one of your own jobs, like a repeat no-cool or a leak after a repair, that was your mistake.

   Everyone has callbacks. You want the person who finds the cause and changes a habit.

   Follow-ups

   • How did you find out it was your mistake?
   • What did you do for the customer?
   • What do you do differently now?

   5Strong

   Owns the specific mistake, explains the root cause, made it right for the customer, and changed a habit to prevent it.

   3Mixed

   Admits the callback but explains it mostly as bad luck or a bad part, with a vague lesson.

   1Weak

   Says they never get callbacks, or blames parts or the customer.

10. Situational · Running the day

    It's late on a July afternoon. Your repair needs a part that isn't on the truck, and dispatch wants you at a no-cool across town. What do you do?

    It shows whether they keep the office and the customer informed, or go quiet when the day gets hard.

    Follow-ups

    • Who do you call first, and what do you tell them?
    • What do you leave the first customer with?
    • What would make you push back on dispatch?

    5Strong

    Tells dispatch right away with what the part is and how long it will take, makes the first customer safe and comfortable for now with a clear return time, notes it all in the software, and heads to the next call.

    3Mixed

    Handles the customer well but tells dispatch late, or leaves without a return time.

    1Weak

    Goes quiet, leaves the customer without a plan, or refuses the next call without a reason.

Work exercise: diagnose a training unit

Set up a training unit in your shop with [two] planted faults a technician can prove with the power off: a weak run capacitor and a loose wire on a condensing unit, or an open igniter and a cracked pressure-switch hose on a furnace. Hand finalists a made-up service ticket and [30] minutes. They use their own meter, talk through each step and follow your lockout rules. Gas stays off. Power goes on only if your safety rules allow it and a supervisor stands by.

Use made-up materials, never real customer work, and keep it to the time shown. Follow your own safety rules for anything hands-on.

Reference check questions

Tell finalists you'll call a former manager, and get their permission first. Ask about what they did, not whether they were nice.

• Tell me about a time they stopped a job or shut equipment down for safety. How did they handle the customer?
• How often did their repairs come back, compared with your other technicians?
• What did customers say about them by name, good or bad?
• Would you hire them again, and what would make you hesitate?

Questions to skip, and what to ask instead

Ask only what the job needs. Questions that touch age, health, family or pay history can break federal, state or local law, even when you mean well.

• SkipCan you handle hot attics all day at your age?

  AskAsk every candidate the same way: this job includes work in attics, crawl spaces and on roofs in summer and winter. Can you do those tasks, with or without reasonable accommodation?

• SkipHave you ever been hurt on the job or filed a workers' comp claim?

  AskWalk me through how you set up to work safely on a roof or in an attic.

• SkipWhat are you making at your current shop?

  AskThis role pays [range and pay plan]. How does that compare with what you're looking for?

• SkipDo your kids make on-call hard?

  AskOn-call is [one weekend a month and some weeknights in season]. How would that work for you?

Common mistakes when hiring an HVAC technician

• Hiring the confident talker

  Some candidates describe a diagnosis beautifully and can't do one. The work exercise shows you the difference in half an hour.

• Letting a certificate stand in for skill

  An EPA Section 608 card shows they passed a test on refrigerant rules. It doesn't show they can find a fault, braze a tight joint or pull a clean vacuum. Treat the card as the minimum and let the questions and the exercise test the rest.

• Skipping the references in peak season

  When the board is full, it's tempting to hire on the spot. Ten minutes with a former service manager about callbacks and customers is the cheapest check you'll ever run.

HVAC technician interview FAQ