Usually worth repairing
- A failed capacitor or contactor, two of the most common cooling repairs
- A fan motor in the indoor or outdoor unit
- A blocked condensate drain or failed condensate pump
- A thermostat or wiring fault
- A refrigerant leak that can be found and repaired at an accessible fitting
Often time to replace
- The compressor has failed on an older system
- The indoor or outdoor coil is leaking in more than one place
- The system uses R-22, a refrigerant no longer produced for servicing
- Repairs have become a regular event
- The system never kept the house comfortable, even when it was working
Weighing the two
A useful way to think about it is to compare the repair against what the system has left to give. A modest repair on a system in good shape is money well spent. A major repair on an old system buys time, but the next failure may not be far behind.
Replacing only the outdoor unit and keeping an old indoor coil is sometimes offered as a middle path. The two halves are designed to work as a matched pair, so it is worth asking how a mismatch would affect efficiency and reliability.
What to ask before deciding
Which part failed and why, the general condition of the rest of the system, whether the refrigerant it uses is still readily available, and whether the house has comfort problems a new system could address. With those answers, the decision is usually clear.