Indoor Heat Exchanger Temperature Sensor Error

Home Appliance Error Codes Fujitsu Split AC

Can you still use it? With care until repaired

Who can fix it? Needs a technician

Typical repair time 30 minutes – 3 hours

Typical cost SAR 80 to 1,200

What it means

This code appears on Fujitsu General split and ducted units on the wired remote or indoor display; older models show it as a number of indicator lamp blinks instead of a number. It means the board reads an impossible value from the indoor heat exchanger (coil) temperature sensor, which points to an open or shorted circuit; this sensor protects the indoor coil from freezing in cooling and controls the fan in heating. Without this reading freeze protection is lost, so the unit usually stops until the fault is repaired. The same number can mean something different on other brands.

Models covered: Fujitsu General (Fujitsu, O General) split and ducted units that show a two-digit error code on the wired remote or indoor display; older models show errors as lamp blink counts instead.

Symptoms4

Cooling stops or weakens and the code shows or the indicator lamps blink.
The unit runs briefly and then stops.
The unit does not return to normal after a restart.
The indoor fan may keep running without cooling.

Possible causes5

A loose or unplugged indoor heat exchanger (coil) temperature sensor connector on the board.
A failed indoor heat exchanger (coil) temperature sensor whose resistance no longer matches the manufacturer table.
A cut or chafed sensor wire from heat, rubbing or rodents.
Corrosion at the sensor or connector from constant condensation on the coil.
A fault in the sensor input circuit on the board (less common).

How to diagnose5

Switch off at the breaker for a few minutes, restart and see whether the code returns.
Switch off the power before any check inside the indoor unit.
The technician inspects the sensor clipped to the indoor coil pipe, its wire and its connector on the board.
The technician measures the sensor resistance at the current temperature and compares it with the manufacturer table.
If the sensor and wire are good, the technician checks the input circuit on the board.

How to fix5

Restart the unit after a power-off; a one-off glitch may clear.
Reseat the sensor connector and clean its pins.
Repair or replace a damaged sensor wire.
Replace the indoor heat exchanger (coil) temperature sensor with a part that matches the model.
Repair or replace the board if the input circuit is faulty, then run the unit and confirm the code does not return.

Repair cost

0–200

200–600

600–1,500

1,500+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost stays low when reseating the connector or replacing the sensor fixes it, and rises when the board has to be replaced.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions

Why does the unit stop instead of running without the sensor?

Without the coil reading, the unit cannot stop the coil from freezing, and a frozen coil can send liquid back to the compressor.

Does a dirty coil cause this code?

No. Dirt affects airflow and temperature, but code 42 means the sensor reading itself is impossible.

Was this explanation helpful?

Tap the stars to rate; you can change it later.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

Report a mistake

Spotted something inaccurate? Tell us and we will review and correct it.