Daikin indoor unit runs but cooling is weak or stops; outdoor unit fan and compressor do not start or stop shortly after starting

Safety first: Refrigerant work must be done by an EPA-certified/FGAS-certified technician. Do not attempt to vent or add refrigerant yourself.

Basic checks you can do:

• Turn off power to the system at the breaker and isolate the outdoor unit.
• Visually inspect the refrigerant lines between indoor and outdoor units for oil stains, corrosion, or physical damage—oil residue often indicates a leak.
• Check flare nut connections at the outdoor service valves and at the indoor unit for signs of oil or looseness. Do not overtighten; note any obviously loose fittings.
• Clean the indoor and outdoor coils with a soft brush to ensure the error is not due to airflow restriction causing abnormal pressures.

What a technician should do:

• Recover remaining refrigerant and perform a nitrogen pressure test and soap-bubble or electronic leak detection on all joints, coils, and service valves.
• Repair or replace leaking components (flare joints, piping, indoor or outdoor heat exchanger).
• Evacuate the system to proper vacuum and recharge with the exact Daikin-specified refrigerant type and weight from the nameplate.
• Clear the error by cycling power and verify normal operation and pressures.