Terminal HVAC units are cheap enough individually that replacement feels easy and numerous enough that replacing on instinct gets expensive fast. A consistent rule is worth more than a case-by-case judgment call.
Repair usually wins when
The cabinet, coils and drainage are sound; the failure is a discrete component such as a fan motor, control board, thermostat or capacitor; the unit's temperature performance has been stable; and parts are available.
A well-maintained unit with one failed part is worth fixing.
Replacement usually wins when
Coils or the cabinet are corroded, the drain pan is damaged, performance has been degrading across successive inspections, the unit has a repeated repair history, the compressor or refrigerant circuit has failed, or parts are no longer obtainable.
Stacking repairs on a unit in that condition rarely buys much time.
Think in groups, not single units
In multi-unit properties, equipment tends to have been installed in batches. When a batch starts failing, planning a phased replacement of that batch is usually cheaper and far less disruptive than replacing units one at a time as they fail.
Let the record decide
This is the practical argument for condition reporting: the repair-versus-replace decision is easy when performance readings and condition notes from previous visits are sitting in front of you, and it is guesswork when they are not.
Want to know the condition of your equipment inventory?
A-TAC maintains PTAC, VTAC, water-source heat pump and mini-split systems across the NYC metro area — New York City, nearby New Jersey, Westchester and Long Island. We can assess a representative sample of units or the full inventory and report what we find.