If there is a demand and the controller indicates an operation command but the compressor does not start, the inspection must differentiate between a control problem and a power problem.
Inverter or contactor
Depending on the unit type, it is checked whether the power stage is actually supplying voltage to the compressor.
Protection state
The compressor may be in minimum off-time, thermal protection, or another temporary lockout.
Communication
In inverter units, a communication fault between the main board and the inverter board may prevent startup.
Diagnosis
Check inverter codes, DC bus, power supplies, and electrical protections only by a qualified technician.
