A quick and sure repair follows the same order every time. Doing every stage avoids replacing the wrong part and being called back.
1. The call: ask the right questions
- What the unit shows: the code on the display or remote, which lamp blinks, how many times.
- Since when, and when: at start, after a while, only on hot days, after a power cut, after cleaning or moving the unit.
- The indoor and outdoor models (photo of the labels), the year of installation, earlier repairs.
2. Safety and a first look
- Switch off before opening a cover; let the outdoor board's capacitors discharge.
- Look before you measure: burnt wires, loose connectors, insects on the board, oil at refrigerant joints, dirty coils, a blocked drain.
3. Read the code and the lamps
Write the code down and look it up for the right brand and exact model - one code can mean different things in different generations. Power off for a few minutes and on again to see whether it comes back.
4. Narrow it down
From the code and the symptoms, put the fault in one of four groups: power supply, control / communication, mechanical (fans, compressor, valves), refrigerant circuit. Each group has its own order of checks - see the guides below.
5. Measure from easy to hard
- Supply, fuses, connecting wires, connectors.
- Sensors and parts you can measure removed (resistance, continuity, insulation).
- Signals with the unit running (voltage, current, pressure) - against the exact model's manual.
- Boards: call a board faulty only when everything around it passes.
6. Repair or replace
- Use the right part or an equivalent the maker allows; keep the wiring, clips and insulation as fitted.
- Refrigerant: find and fix the leak first, evacuate, charge the type and amount on the label.
7. Test run and operating values
- Run long enough for the unit to settle; check the code does not come back.
- Measure the running current, the outlet air temperature, the pressure (if the circuit was opened) and compare with the manual.
8. Clean up, hand over, write it down
- Refit every cover and screw; clean the work area.
- Tell the customer the cause and how to avoid it.
- Note the model, the code, what you measured and replaced - the next repair goes faster.
In the app: look the code up at stage 3, and use Service manual chat to ask how to check each part, the values and the repair procedure from the service manuals at stages 4-7.
Safety: switch off both the indoor and the outdoor unit before opening a cover or touching a board; the capacitors on the outdoor board stay charged for a while after power-off - wait for the board's lamps to go out and measure before touching. Refrigerant and high-voltage work belongs to a certified technician.