Aircon Outdoor PCB
The outdoor PCB controls compressor operation and handles the communication between indoor and outdoor units. When it fails, the indoor unit may look completely normal — but cooling never happens. This is one of the easiest faults to mistake for a dead compressor.
What This Part Does
The outdoor PCB is the controller for your outdoor unit. It receives start commands from the indoor unit, then drives the compressor and outdoor fan.
It also handles safety logic — temperature limits, protection cutouts, and fault codes. If a protection event happens, the board decides whether to stop or continue.
Without a working outdoor board, even a perfectly healthy compressor will not run. The compressor cannot start itself.
How You Would Notice
The indoor unit runs. The fan blows. The display looks normal. But the room stays warm.
The outdoor unit may be completely silent — no compressor hum, no fan. Or it may start briefly then stop.
In some cases error codes appear on the indoor display, but they do not always clearly identify the outdoor board as the cause.
- Indoor unit and fan run normally but no cooling arrives
- Outdoor unit is silent or stops immediately after startup
- Fault light flashing on indoor unit without a clear error
It Might Not Be The Board
A faulty compressor produces the same symptom. The indoor unit runs, the outdoor unit tries to start, but cooling never happens.
A wiring fault between indoor and outdoor units can also block the start command before it reaches the board.
We check communication first, then board output, then the compressor. The cheapest confirmed answer comes first.
How We Check
We check the indoor-outdoor communication path first. A broken signal wire stops the start command before it reaches the board.
If communication is intact, we check board output. The board should receive the start command and deliver power to the compressor.
If the board receives the command but does not deliver output, the board is confirmed failed.
If the board delivers output but the compressor does not respond, we move to compressor diagnostics.
What We Find And What Happens Next
We work through the signal chain in order. Each step is cheaper than the next.
| Finding | Next Step |
|---|---|
| Communication path fault | Repair wiring, retest |
| Board output failure confirmed | Replace outdoor PCB |
| Board output normal, compressor not responding | Compressor diagnosis |
About The Repair
Outdoor PCB replacement is a moderate-to-major repair. The board is brand and model specific.
If a technician recommends compressor replacement before checking board output and communication path, ask what the output measurements showed.
A confirmed board fault should be provable with measurements. No measurement means no confirmed fault.
After Replacement
A replaced outdoor board should restore normal compressor and fan operation. Cooling should arrive promptly after startup.
If the fault is intermittent, run the replacement board under hot conditions before closing the job.
We run a post-replacement load test before confirming the repair is complete.
When We Tell You To Wait
If the fault is intermittent and the unit cools most of the time, the issue may be heat-related board instability rather than full failure.
Tracking when failures happen — after extended runtime, in direct sun, in specific weather — gives useful diagnostic data.
We will tell you on-site what the checks show before recommending any replacement.