Every vendor calls their service "preventive maintenance." What matters is the checklist behind them — and whether it's the same consistent checklist.
Ask ten technicians what a PM visit covers. You'll get ten different answers. One checks the filter and calls it done. Another checks filter, coil, refrigerant charge, and amperage draw, and writes down every number. Both get billed the same. Only one of them prevents anything.
A real checklist does three things.
- It's the same every visit, for every unit, no matter who shows up.
- It produces numbers, not descriptions.
- It gets compared against last visit's numbers, not just filed away.
Sameness matters because maintenance is a trend, not a snapshot. Numbers matter because descriptions hide problems. "Coil looks fine" is a description. "Static pressure: 0.62 in. w.c." is a number. It can be tracked. It can be flagged.
Take a coil cleaning. "Coil cleaned" checks a box. "Static pressure before: 0.71. After: 0.52." proves the cleaning worked. Same visit, same technician. Different accountability.
The fix is simple. Ask for the checklist. Not a description of the program — the real list, with units of measurement, used at every visit. If a vendor can hand you one, and show last quarter's numbers next to this quarter's, you have a maintenance program.
If all they can hand you is a stack of "completed" work orders, you have a cleaning service with a better name.
Field Note
Ask your vendor for the checklist template, blank, before your next visit. If it has no place to write a number, it isn't measuring anything.