Assess the causeFollow the evidence.
Check mode and demand, supply, communication, protective conditions and outdoor components.
The exact model and operating conditions determine which tests apply. These are possible inspection directions, not a list of components that must be changed.
Before the appointmentKeep the useful details.
Tell us whether the outdoor unit ever starts and whether the indoor display shows a code.
Record the timing, previous work and accessible model label. Do not remove covers or handle live, refrigerant or pressurised components to obtain information.