Indoor FCU thermistors feed temperature signals used for fan and cooling control. When those readings drift or drop out, the unit can behave unpredictably. Because these symptoms can look like board or compressor problems, sensor checks should come first.
Most likely when
Often not this
Check first
Primary question
Could a faulty indoor FCU thermistor be causing unstable cooling behavior and bigger replacement recommendations?
Indoor thermistors are mounted around FCU sensing points such as room-air intake and evaporator coil path.
These readings influence FCU control behavior and protect against unstable operating conditions.
When indoor sensor data is wrong, the FCU can behave unpredictably even if larger components are still functional.
Not every unstable cooling pattern is a sensor fault.
Check sensor-path basics first so you do not mislabel a broader issue as a thermistor fault.
Ask for simple evidence that this is a sensor problem, not only a general cooling complaint.
Get urgent help if cooling behavior becomes unstable after recent repair work or changes rapidly from day to day.
Unstable sensor input can lead to repeated callbacks and larger misdiagnosis risk.
Replacement usually makes sense when sensor behavior stays abnormal after airflow, settings, and connector checks are completed.
It usually does not make sense when larger parts are suggested before sensor-path evidence is shown.
Learn indoor FCU PCB fault signs, what they can look like, and what to check before replacing the board.
Learn what outdoor unit thermistors do, what symptoms they can trigger, and what to verify before approving replacement.
Learn what the FCU blower fan motor does, common fault signs, and what to check before saying yes to replacement.
Tell us what is happening. We will assess first, advise one clear next step, and you decide.
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