Maintenance technician screening questions: PLCs, hydraulics, lockout and PM work

Maintenance technician screening questions should find out what the candidate fixes when a line goes down, how they find the fault, and whether they lock out every energy source before they put their hands in. Ask about the last breakdown they solved, the split between electrical and mechanical work, their PLC level and their lockout routine. Those four answers sort a plant technician from a general handyman in about ten minutes.

This page is about industrial maintenance: technicians who keep production equipment running in plants, food and beverage, packaging and distribution. It differs from our HVAC technician questions, which cover building systems and refrigerant certification, and from the electrician questions, which cover license levels and construction wiring. Where a role needs a licensed electrician, use that page as well.

Industrial, facilities or multi-craft: know which job this is

Clients use "maintenance tech" for several roles. Confirm which one before you screen.

Many job orders say "must be strong in electrical and mechanical". Ask the client which half the night shift actually calls about. Most candidates are stronger on one side, and the placement lasts when their strong side matches the plant's most common breakdowns.

Knockout questions

Electrical and PLC questions

PLC claims are the most inflated part of a maintenance resume. Separate three levels: reading the logic online to find which input or output is not changing state, making small edits under supervision, and writing or modifying programs. Most good plant technicians sit at the first level, and that is fine for most roles. The common platforms are Allen-Bradley (Rockwell) controllers programmed in Studio 5000 or RSLogix 500, and Siemens controllers programmed in TIA Portal or Step 7.

1. "Tell me about the last electrical fault you found. What did you check first?"
   • Strong answer: a clear sequence: what the machine was doing, what the HMI or fault code said, which inputs they checked, what they measured with a meter, and what the cause was (a failed prox sensor, a tripped overload, a loose wire at a terminal).
   • Red flag: starts by replacing parts until it works.
2. "Which PLC platform and software do you use, and what do you do in it?"
   • Strong answer: "Allen-Bradley CompactLogix in Studio 5000. I go online and watch the rungs to see which condition is not true. I've added a timer once with the controls engineer watching."
   • Red flag: "I program PLCs" with no software name and no example of a change.
3. "Have you set up or changed parameters on a VFD? Which brand?"
   • Strong answer: names the drive (PowerFlex, ABB, Yaskawa and so on), talks about reading fault codes, changing accel or decel time, or replacing and reloading parameters.
   • Red flag: does not know what a VFD is, for a role with conveyors and pumps.
4. "How do you read an electrical print for a machine you have never seen?"
   • Strong answer: find the fault on the HMI, go to the I/O page for that device, trace the wire numbers back to the terminal and the PLC card.
   • Red flag: never uses prints; relies on memory of a single machine.

Mechanical, hydraulic and pneumatic questions

1. "When did you last replace a bearing or a gearbox, and how did you align it afterwards?"
   • Strong answer: names the method (laser alignment tool, or dial indicators with a rim-and-face or reverse-dial method) and why alignment matters for bearing life.
   • Red flag: "straight edge and eyeball" as the normal method, for a plant with large rotating equipment.
2. "Tell me about a hydraulic problem you solved. How did you find it?"
   • Strong answer: reads the schematic, checks pressure at test points, isolates the pump, relief valve, directional valve or cylinder, and mentions bleeding off pressure before opening anything.
   • Red flag: starts by loosening fittings on a pressurized system.
3. "On a pneumatic machine, what would you check if a cylinder moves slowly?"
   • Strong answer: supply pressure at the regulator, leaks, a sticking valve, flow controls, a worn cylinder seal.
   • Red flag: no idea where air pressure is set.
4. "Do you weld or fabricate as part of maintenance work?"
   • Strong answer: an honest level: "MIG repairs on guards and brackets, nothing structural."
   • Red flag: claims structural welding with no test or code to name. For welding-heavy roles use the welder questions.

Lockout/tagout: what the rule requires and what to ask

OSHA's control of hazardous energy standard, 29 CFR 1910.147, is the rule every plant maintenance technician works under. As of September 2026, it says, among other things:

• An authorized employee is the person who locks or tags out a machine in order to service or maintain it. A maintenance technician is almost always an authorized employee.
• Before starting work on locked-out equipment, the authorized employee must verify that isolation and deenergization have been accomplished.
• In group lockout, each authorized employee attaches a personal lock or tag to the group device when they start and removes it when they stop.
• A lock is removed by the employee who applied it. The exception is a documented employer procedure for when that person is not available.
• The employer inspects each energy control procedure at least annually, and retrains authorized and affected employees when job assignments, machines or procedures change.

The standard is the employer's responsibility, not the candidate's, so your questions should test habit rather than recite the rule. Ask these:

1. "Walk me through locking out a machine that has electrical, air and a raised part held up by a cylinder."
   • Strong answer: notify operators, shut down normally, isolate the electrical disconnect and the air supply, lock each with their own lock, bleed the air, block or lower the raised part so gravity cannot drop it, then try to start the machine to verify zero energy, and return the controls to off.
   • Red flag: hits the e-stop and starts work. The standard says push buttons, selector switches and other control-circuit devices are not energy isolating devices.
2. "What do you do if you find a lock on a machine and the person who put it there has gone home?"
   • Strong answer: leave it and go to the supervisor; the plant's removal procedure decides what happens next.
   • Red flag: cuts it off.
3. "Has a supervisor ever asked you to skip lockout to get the line running faster? What did you do?"
   • Strong answer: a calm refusal and a quick, safe way to still get the line back.
   • Red flag: treats skipping lockout for "quick" jobs as normal.

PM versus breakdown work, and the maintenance system

A plant that only fixes what breaks needs a fast troubleshooter. A plant with a strong preventive maintenance (PM) program needs someone who does the scheduled work properly and records it. Ask which kind of plant the candidate comes from, because the habits differ.

• Reactive or breakdown work: fixing a machine that stopped. Ask for the longest breakdown they worked and how they found the cause.
• Preventive maintenance: scheduled inspections, lubrication, belt and filter changes. Ask how many PM work orders they closed in a typical week and what they wrote on them.
• Predictive work: vibration analysis, thermography, oil analysis. Ask whether they collected the data, read the reports, or both.
• The CMMS: the system that holds work orders, such as IBM Maximo, SAP Plant Maintenance, eMaint, Fiix, UpKeep or Limble. Ask what they recorded in it and whether they created work orders or only closed them.

Some candidates will quote downtime metrics. Mean time to repair (MTTR) is total repair time divided by the number of repairs: for example, 30 hours of repair over 12 breakdowns is 2.5 hours each. If a candidate says they cut MTTR, ask what it was before, what it was after, and what they changed. An improvement with no starting number is a story, not a result.

Shifts, on-call, tools and pay

• Shift pattern: fixed shifts, rotating shifts or 12-hour patterns are common in continuous plants. Confirm which one and whether the candidate has worked it.
• On-call and shutdowns: how often they are called in, and whether planned shutdowns on holiday weekends are expected.
• Tools: which hand tools and meters they own, and whether the plant supplies the rest.
• Pay: base hourly rate, shift differential and overtime pattern. A technician on heavy overtime will quote annual earnings; compare base rate to base rate, then discuss overtime separately. The salary expectation questions guide has wording.
• Why they are moving: "Tired of being the only tech on nights" and "want to learn PLCs" are useful answers; both tell you what the next plant must offer.

How maintenance experience gets overstated, and a scoring rubric

• "PLC programming" means going online to watch the logic. Useful, but not programming. Ask for the last edit.
• "Hydraulics" means changing hoses. Ask them to describe reading a schematic.
• "Industrial maintenance" was facilities work in an industrial building. Ask what production equipment they touched.
• "Lead technician" was the only technician on the shift. Ask how many technicians they directed.
• Years of experience include a helper or apprentice period. Ask how long they have worked breakdowns alone.

If a hiring manager and a recruiter both screen, ask the same five areas in the same order so the scores compare. Interview Signal builds that guide from the job description and ticks off each question as it is covered, so the lockout question is not the one that gets skipped when the PLC story runs long.