Ask about one actual work decision
Begin with: “How do you distinguish poor airflow from a refrigerant-circuit issue before replacing parts?” Ask what evidence the person had, what they checked, who authorized the work and how they knew the result was acceptable. The same question can reveal disciplined process at different experience levels.
Probe an ambiguous situation
Give an ordinary scenario such as rooftop unit controls complaint. Ask what information they would gather before changing anything. Reward candidates who identify missing facts and boundaries. Do not turn the interview into a test of dangerous improvisation or ask them to describe bypassing safeguards.
Separate tasks from titles
Someone who has worked around residential service calls may not have led a project involving new-installation and commissioning projects. Ask which specific tasks they performed personally, which they assisted and which they have only seen. In a hiring process, clear limits are useful information, not grounds for embarrassment.
Check documentation and communication
Ask them to explain how they would record a handoff after no-cooling service call with restricted airflow. Could the next shift understand what happened? Would a customer or inspector understand the result? This helps distinguish candidates who complete work from candidates who can make the work verifiable.
Finish with mutual clarity
Tell candidates the actual shift, travel demands, supervision and tools supplied. Summer peak workload, emergency rotations and truck policies matter in the offer. Use the same essential questions for every comparable applicant, document role-related reasons for decisions and avoid asking for protected personal details.