The difference between a visit and a service
Plenty of maintenance visits amount to a filter change and a look. They take forty minutes, the customer sees somebody arrive and leave, and nothing is learned about the equipment. Those are the contracts that do not renew, and rightly so.
A real service produces information. Not just 'cleaned and tested' but numbers that can be compared with last time, so that a slow decline becomes visible months before it becomes a breakdown. That is the entire argument for preventive maintenance, and it only works if somebody writes the numbers down.
The core checks
The specifics vary by equipment type, and the manufacturer's requirements always take precedence, particularly where warranty is involved. But across most comfort cooling and light commercial plant, the same families of check recur.
- Electrical: tightness of connections, signs of overheating or arcing, contactor condition, capacitor condition, insulation where appropriate, and running current compared with nameplate.
- Refrigeration circuit: operating pressures, superheat and subcooling, sight glass condition, and any sign of oil staining that suggests a leak.
- Air side: filter condition and replacement, coil cleanliness on both sides, fan and belt condition, airflow and temperature split across the coil.
- Condensate: tray, trap and drain clear and draining, pump operating where fitted. A blocked condensate drain causes more water damage claims than almost anything else on this list.
- Controls and safeties: thermostat or BMS operation, setpoints as the customer expects, high and low pressure cut-outs, and any alarm history on the controller.
- Structural and environmental: mounts, vibration, insulation condition, guards, and anything obstructing the condenser that has appeared since last time.
Record readings, not adjectives
'Pressures OK' is worth nothing in six months. The actual figures are worth a great deal, because the second and third visits turn them into a trend. A suction pressure drifting down across three visits is a leak being found early; the same leak found by a breakdown call in August is an emergency, a loss of refrigerant, and a very unhappy customer.
This is the single highest-value change most companies can make to their maintenance work, and it costs nothing but discipline: capture numbers in the field, against the specific unit, every time.
Record against the unit, not the visit
A site with eleven units and a maintenance history filed by date is a history nobody can use. The question a technician asks is never 'what happened on site in March', it is 'what has this unit been doing'.
Keeping the record against the asset : nameplate details, serial number, location, refrigerant type and charge : is what makes a two-year-old reading findable. It is also what makes the refrigerant records required in a growing number of jurisdictions possible to produce without an archaeology expedition.
Finish with a recommendation
The most valuable part of a maintenance report, to the customer, is the last line: what you think should happen next. A failing contactor flagged in February is a planned replacement; the same contactor in July is a site shutdown.
It is also how maintenance contracts generate additional work honestly. You are not selling: you are reporting what you found, with the readings underneath it, and letting the customer decide with good information.