Aircon Indoor PCB
The indoor PCB is the control board inside your indoor unit. When it fails, the unit may beep, respond to the remote, and show normal display — but cooling never starts. A wiring or sensor fault can look identical.
What This Part Does
The indoor PCB is the brain of your indoor unit. It reads the temperature sensors, interprets your remote commands, and sends start signals to the outdoor unit.
When it works, you press cool on the remote and cooling starts. When it fails, the board may beep and show input — but fail to send the start signal.
The board manages the fan speed, reads the thermistor, and maintains the communication link to the outdoor unit.
How You Would Notice
The most confusing pattern: you press the remote, it beeps, the display changes — but the compressor never starts. The indoor fan may run but no cooling arrives.
In some cases the unit behaves normally for days, then randomly fails to start.
Error codes may appear, but they do not always clearly point to the board.
- Remote beeps and display responds but cooling does not start
- Fan runs at correct speed but no cold air arrives
- Intermittent behavior — works sometimes, fails other times
It Might Not Be The Board
A loose signal wire or corroded connector can interrupt the start command without the board failing. The symptoms look the same.
A faulty indoor thermistor can also stop the cooling cycle — the board is working but getting wrong temperature data.
We check the wiring and sensor before we look at the board.
How We Check
We check wiring and connectors first. A loose or corroded pin can stop the signal path without the board failing.
We test the indoor thermistor. A sensor feeding wrong data can stop the cooling cycle without any board fault.
If wiring and sensor check out, we measure the board's output signal. A board that receives input but fails to send a valid start command is confirmed failed.
We replace the board only when output failure is confirmed after ruling out simpler causes.
What We Find And What Happens Next
Most beep-but-no-cooling cases are resolved by a wiring or sensor fix. Board replacement is needed when output measurement confirms failure.
| Finding | Next Step |
|---|---|
| Wiring or connector fault found | Repair connection, retest cooling |
| Thermistor reading off | Replace sensor, retest |
| Board output failure confirmed | Replace indoor PCB |
About The Repair
Indoor PCB replacement is a moderate-to-major repair. The board is specific to the model and brand, so sourcing time varies.
If a technician recommends PCB replacement without checking wiring, connectors, and the thermistor first, ask what was measured.
Board replacement should be the last step, not the first guess.
After Replacement
A replaced board should restore normal operation immediately. The unit should respond to remotes and start cooling reliably.
If intermittent failure continues after board replacement, the wiring path or connectors may still have an issue.
We confirm stable operation over a test run before closing the job.
When We Tell You To Wait
If the unit works most of the time with occasional failure, the cause may be a loose connector or intermittent sensor. Not a failed board.
Tracking when failures happen — after long runs, in certain weather, with specific modes — helps narrow the cause.
We will tell you on-site what the checks show before recommending anything.