What to Check on a Maintenance Visit (Generic)
Why this matters
A maintenance visit is only worth what you find on it. Two techs can both "do the PM," but one leaves with three problems caught early and a happy customer, while the other just wiped down the unit and moved on. The difference is a repeatable method. This card gives you the generic inspection logic that applies whether you are servicing a heating unit, a water system, an electrical panel, an appliance, or a pump. Adapt the specifics to your trade, but the order and the senses stay the same.
Use all your senses first
Before you open anything, stop and observe the equipment running. Your eyes, ears, nose, and hands catch faults no meter will show you on a cold unit.
- Look for stains, drips, corrosion, scorch marks, loose mounting, and anything out of place from its normal position.
- Listen for new noises: grinding, buzzing, rattling, clicking, or a pitch that is higher or rougher than normal.
- Smell for hot insulation, burning, fuel or refrigerant odor, or anything sharp and chemical.
- Feel for excess heat, abnormal vibration, and looseness in things that should be tight (with power and pressure handled safely first).
Write down what is normal. The first visit sets the baseline; every visit after compares against it.
The five PM actions
Most preventive work is some combination of five actions. Run the equipment through this list:
- Clean. Dirt is an insulator and a flow restrictor. Clear filters, coils, screens, vents, and intakes. A dirty surface makes everything run hotter and work harder.
- Tighten. Vibration loosens connections, fasteners, and terminals. A loose electrical terminal arcs and burns; a loose mount destroys bearings. Re-torque what the equipment specifies.
- Lubricate. Moving parts that should be greased or oiled, on the schedule the equipment calls for, not more and not less. Over-greasing causes its own failures.
- Adjust. Belts, alignments, set points, and clearances drift over time. Bring them back to spec.
- Replace wear parts. Filters, seals, and consumables that are partway through their life and not worth leaving for the next failure.
Check the things that fail
Spend your attention where failures actually start, not where they are easy to reach:
- Electrical connections and contacts. Discoloration, pitting, and heat at a terminal predict a burned connection. This is the single most common preventable electrical failure across trades.
- Moving and rotating parts. Bearings, motors, and anything that spins gives early warning through noise, heat, and play. Grab and wiggle (safely) to feel for slop.
- Seals and gaskets. Any boundary holding back water, air, fuel, or refrigerant. Look for the residue trail a slow leak leaves.
- Wear surfaces. Belts, contactors, and parts that rub or cycle. Read the wear pattern; uneven wear means a misalignment upstream.
Read the wear signs, not just the part
A worn part is a symptom. The skill is asking why it wore. A belt that frays on one edge points to misalignment. A contact that pits points to an electrical problem feeding it. A seal that fails early points to vibration or heat it should not see. If you replace the part and not the cause, you are booking the same callback.
Document and report
Close every visit by writing down readings, what you found, what you fixed, and what you flagged for later. A finding the customer never hears about is a finding wasted. Tell them plainly: what is healthy, what you watched, and what needs attention before it becomes an emergency. That report is also your defense if something fails after you left, and it is the baseline for the next tech.
References
- Manufacturer documentation: equipment-specific maintenance checklists and service intervals
- OSHA general industry guidance on inspection and safe maintenance practice
- Trade-standard preventive-maintenance practice across mechanical and electrical systems
- See related: Documenting a Maintenance Baseline; Spotting a Failure Before It Happens