Daikin air conditioner stops during operation; indoor unit may show U2 and system will not restart until power is cycled

Safety first: Turn off the breaker before opening any electrical covers. If you are not comfortable with electrical measurements, contact a qualified electrician or HVAC technician.

User-level checks:

• Confirm that the correct breaker is ON and not tripping. Reset once if tripped; if it trips again, do not continue resetting.
• Check that no high-power appliances (ovens, welders, large motors) are sharing the same circuit and causing voltage dips when starting.
• Inspect the outdoor unit area for rodent damage or visible burnt wiring (without removing covers if this voids warranty).

Technical checks (for a professional):

• Measure supply voltage at the outdoor unit terminal block while the unit attempts to start; compare with Daikin specifications (typically 220–240 V or 110–120 V depending on model).
• Tighten all terminal screws at the outdoor unit and indoor unit line-voltage terminals.
• Inspect the outdoor power PCB for burnt components, swollen capacitors, or discoloration; replace the power PCB if defective.
• Verify correct wire gauge and cable length per Daikin installation manual to avoid excessive voltage drop.