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HVAC Technician Interview Questions

An HVAC interview is really a service manager deciding whether they can send you alone into a stranger's attic. They'll test how you troubleshoot, how you handle refrigerant, and how you talk to a homeowner who's been sweating since last night. Here's what gets asked and what a good answer sounds like.

12 questions9 minute read

Part 1

1.Walk me through a no-cool call on a residential split system, from the driveway to the invoice.

Why they ask

This is the call you'll run more than any other in summer. They want to hear a repeatable order, not a guess that starts at the most expensive part.

How to answer

  • Start with the customer: what they noticed, when it started, whether anyone's been out before
  • Check the thermostat and the air filter first, then confirm the indoor blower is running
  • At the condenser, check for power, the disconnect, the contactor and the capacitor before touching refrigerant gauges
  • Only then take pressures and temperatures, and explain superheat or subcooling against the metering device
  • Close with what you told the customer, the options you gave, and how you wrote it up

2.How do you tell a bad capacitor from a bad compressor?

Why they ask

Condemning a compressor is a big bill for the customer and a warranty headache for the shop. They need to know you don't get it wrong.

How to answer

  • Kill power and discharge the capacitor safely before testing it
  • Read microfarads with your meter and compare to the rating on the label
  • Check compressor windings for resistance between common, run and start, and check for a short to ground
  • Consider a tripped internal overload on a hot compressor, and give it time to reset before you condemn anything
  • Mention you'd get a second opinion or use a hard-start kit test before calling it dead

3.Tell me about your EPA refrigerant certification and how you handle recovery.

Why they ask

Venting refrigerant can get the company fined, and they can't legally let an uncertified tech work on sealed systems. They're also checking whether you actually follow the rules when nobody's watching.

How to answer

  • Name which EPA certification type you hold (Universal is what most shops want) and have the card with you
  • Describe recovering into a properly rated, labeled cylinder with a recovery machine, never venting
  • Talk about keeping refrigerants separate and not overfilling the recovery tank
  • If your state or city needs an HVAC or mechanical license, say what you hold and that you know the local rules differ
4.A heat pump is running but the house won't get warm on a cold morning. What are you checking?

Why they ask

Heat pumps confuse a lot of newer techs and a lot of customers. They want to see you understand defrost, auxiliary heat and the reversing valve.

How to answer

  • Check the thermostat is set for heat pump and that auxiliary or emergency heat is wired and working
  • Look at the outdoor coil for ice buildup and whether the unit's going into defrost
  • Test the defrost board, sensor and the reversing valve solenoid
  • Check the heat strips and their sequencers or breakers in the air handler
  • Explain to the customer that a heat pump's supply air feels cooler than a furnace's, so they don't think it's broken when it isn't
5.What's in your truck, and what tools do you own versus expect the company to supply?

Why they ask

It tells them your experience level fast. It also sets expectations, since some shops expect you to bring your own hand tools and some don't.

How to answer

  • Name your basics: a good multimeter with a clamp, digital manifold or gauges, a thermometer and probes, a vacuum pump and micron gauge
  • Mention a nitrogen setup for pressure testing and brazing if you do installs
  • Say how you keep the truck stocked (capacitors, contactors, filters, fuses) so you fix it on the first visit

Part 2

6.How do you know an evacuation is done properly before you charge a new system?

Why they ask

Moisture and air in a new system cause failures that show up months later as callbacks. This question separates careful installers from fast ones.

How to answer

  • Pressure test with dry nitrogen first and check for leaks with soap bubbles or an electronic detector
  • Pull down with a vacuum pump and read it with a micron gauge at the system, not at the pump
  • Do a decay test: isolate the pump and watch whether the reading holds or climbs
  • Explain what a rising reading means (a leak or moisture still boiling off) and what you'd do about it
7.Tell me about a callback you caused. What happened and what did you change?

Why they ask

Every tech has had one. Callbacks cost the shop a truck roll and a customer's trust, so they want someone who owns it instead of blaming the part.

How to answer

  • Pick a real one and say plainly what you missed
  • Explain how you found out and how you handled the customer on the second visit
  • Describe the habit you built afterward, like checking the drain line on every cooling call or rechecking amp draw before leaving
8.A homeowner says the last company quoted them a full system replacement. You think it just needs a repair. What do you do?

Why they ask

Shops that sell on commission worry about techs who never recommend replacements. Honest shops worry about techs who always do. They want to see your judgment and your ethics.

How to answer

  • Diagnose it yourself before you say anything about the other company
  • Give the customer the repair option and its cost, and be straight about the age and condition of the system
  • Offer replacement as an option if the equipment's near the end of its life, without pressure
  • Let the customer choose and document what you told them
9.What's your experience with gas furnaces, and how do you check for safe combustion?

Why they ask

A furnace mistake can put carbon monoxide in someone's house. They need to trust you on gas work more than anything else.

How to answer

  • Walk the sequence of operation: call for heat, inducer, pressure switch, ignitor, gas valve, flame sensor, blower
  • Check gas pressure with a manometer against the nameplate
  • Inspect the heat exchanger and venting, and use a combustion analyzer if the shop has one
  • Say you'd shut the unit down and red-tag it if you found a cracked heat exchanger or a CO problem, and explain it clearly to the customer
10.It's a heat wave and you've got more calls than time. How do you work your board?

Why they ask

Peak season is when shops make their year and when techs burn out. They want someone who stays steady and communicates with dispatch.

How to answer

  • Follow dispatch priorities, and flag safety calls (elderly customers, medical needs, no heat in a freeze) right away
  • Keep customers updated when you're running late instead of going quiet
  • Don't cut corners on diagnosis to go faster, since callbacks make the week worse

Part 3

11.Have you worked with a service app like ServiceTitan or Housecall Pro? How do you write up a job?

Why they ask

The office bills from your notes. Vague write-ups cause billing fights, warranty denials and confused techs on the next visit.

How to answer

  • Name the software you've used, or say you learn these tools quickly if you haven't
  • Describe notes that list what you found, what you replaced, readings you took and what you recommended
  • Mention photos of the nameplate, the failed part and the finished work
  • Say you get customer signatures and payment before leaving when the shop wants it
12.Why do you want to work here instead of the shop down the road?

Why they ask

Good techs get recruited constantly. They want to know whether you'll stay past the first busy season.

How to answer

  • Mention something specific: their training, their mix of residential and commercial, their on-call rotation, their trucks
  • Say what you want to learn next, like commercial rooftop units or controls
  • Be honest about what matters to you in a shop, like fair dispatching and support on tough calls

Questions to ask them

Ask at least two. It shows you're picking them too.

  • How does the on-call rotation work, and how often will I be on it during peak season?
  • Do techs get paid for callbacks, and how does the shop decide whose callback it is?
  • Is there a sales commission or spiff on replacements, and how much pressure is there to sell?
  • What training do you offer for newer techs, and can I ride with a senior tech before running calls alone?
  • Do I take the truck home, and who's responsible for stocking it?
Career guideWhat a HVAC Technician does, and what it pays
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Skills to learnHVAC Technician skills: what to learn first
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